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Each slice of this easy egg breakfast casserole is thick, flavorful, and satisfying; plus, the recipe is an incredibly convenient breakfast choice since it’s make-ahead and infinitely adaptable. Like quiche, you can use your favorite seasonings and cheeses, vegetables like peppers and mushrooms, meats like sausage or bacon, or you can make it vegetarian. The best part is that you can assemble this dish ahead of time so breakfast is a breeze in the morning!

breakfast egg casserole with peppers, spinach, mushrooms, and cheese.

Breakfast casserole is an all-in-one hearty meal that can be made ahead of time, feeds a crowd, reheats well, and makes great leftovers. My family devours it. For all these reasons and more, I’ve made it nearly 100x (no exaggeration there) for breakfast, brunch, and, yes, dinner.

I originally published this recipe in 2015 and have simplified it over the years. Let me show you how it comes together so you too can experience this crowd-pleasing superhero meal.

This Easy Breakfast Casserole Is:

  • Adaptable to whatever vegetables, meats, cheeses, and herbs you have on hand.
  • Easy to make ahead of time.
  • Quick to throw together.
  • Great as a quick weekday meal or a lavish weekend or holiday brunch.
  • Excellent for entertaining a crowd.
  • Made with some bread to soak up moisture, but potatoes work too!
  • Ready for your favorite egg toppings like salsa, pico de gallo, green onion, cilantro, parsley, avocado, everything bagel seasoning, hot sauce, etc.
slice of egg and sausage breakfast casserole on green plate.

4 Main Components

When gathering ingredients for this recipe, I like to think of it as having 4 separate components. From there, you can have fun with variations.

  1. Vegetables
  2. Meat (or extra vegetables)
  3. Starch for soaking up moisture
  4. Egg, cheese, & milk mixture

Here Are the Endless Add-ins & Flavor Options

  1. Vegetables: Select which vegetables you’d like in the dish. Generally, the most popular with guests is bell peppers, spinach, and mushrooms. But I’ve also made this with broccoli/peppers, kale/mushrooms, and spinach/zucchini. Try to stick to 3–4 cups of vegetables total. Cook the vegetables down with some flavor-enhancing onion and garlic.
  2. Meat: Guests usually prefer meat in the casserole, so I add sausage. Or try using ground turkey, diced bacon, ground beef, or ground chicken. I usually purchase uncooked sausage for this and brown it with some dried rosemary or Italian seasoning to give it a little extra flavor, but that is optional. If the meat you’re using is pre-cooked, such as diced ham or shredded chicken, you can mix it with the cooked vegetable mixture before layering it into the dish.
  3. Starch: Like when making breakfast strata, sausage stuffing, and cream cheese French toast casserole, the bread should be slightly stale so it can soak up moisture. Crusty sourdough is FANTASTIC here. You can also use homemade artisan bread, a loaf of French bread, crusty baguette, biscuits, bagels or homemade bagels, or even day-old croissants (have you tried homemade croissants?!). To make it gluten free, use gluten-free bread or potatoes.
  4. Eggs, milk, & cheese: Whisk a dozen eggs with a little half-and-half or milk and stir in some shredded cheese. Like the vegetables and meat, use whatever cheeses you like best, such as sharp cheddar, pepper jack, feta, and/or smoked gouda.

Variations: One of my favorite variations of this recipe is everything bagel breakfast casserole. It’s a BIG HIT and consistently gets rave reviews. Or try my different method/recipe for biscuit breakfast casserole with homemade biscuits baked right on top.

eggs, half-and-half, spinach, garlic, sausage, cheese, peppers, and other ingredients.

Can I Use Potatoes?

Yes, you can replace the bread with diced hash brown potatoes—the kind you find in the freezer section of the grocery store. Guests have *loved* this version. Use about 3 cups (around 380g) of hash browns in place of the bread. You could also peel and dice fresh potatoes, but you’ll need to quickly cook them on the skillet for 10 minutes before using in this dish.

Do I Have to Use Bread?

Bread or potatoes, yes. Besides eggs, bread is the main ingredient. To avoid a spongey, wet dish, this breakfast casserole needs structure at the bottom. You see, when eggs bake, they release a lot of liquid. Chunks of crusty bread (or hash brown potatoes) soak up some liquid so the casserole is chunky and textured, not flat and wet. If you’re looking for something without this starchy addition, crustless vegetable quiche is a great option.

In Pictures: How to Make Breakfast Casserole

First, place the pieces of bread (or potatoes) in the bottom of a greased 9×13-inch or any 3–4-quart oven-safe dish. I usually use (affiliate links) this glass pan or the pictured red ruffled baking dish, which comes in a set with other sizes—definitely a splurge, but I’ve found the quality to be excellent. Showing you the bread scattered in the pan as well as the optional potato substitution:

chunks of bread and potatoes shown separately in bottom of red casserole dish.

Set that aside and pre-cook your vegetables and meat (if the meat is not cooked already). You can do this all in 1 big skillet on the stove, adding onion, garlic, and optional herbs like dried rosemary or your favorite seasoning blend. As that’s sizzling on the stove, whisk the eggs, milk, and cheese together:

Now it’s time to assemble, and I’ve made this process a lot easier over the years. Spoon all of the vegetables/meat mixture on top of the bread. Pour the egg mixture all over that:

Success Tip: Refrigerate Overnight

At this point, you can either bake it right away or refrigerate the casserole overnight and for up to 24 hours. During this time, the flavors mingle together and the bread has a chance to soak up some of the liquid and flavor. Wake up and all you have to do is slide it into the oven. If you’re in a rush, I do recommend at least 30 minutes in the refrigerator before baking, if you can spare it!

Bake until the edges are golden brown. Because it’s so egg heavy, the casserole puffs up in the oven like a cheesecake and then sinks back down as it cools. Cool for 5–10 minutes before slicing and serving.

overhead photo of egg and sausage breakfast casserole in red baking dish.
overhead photo of slice of egg breakfast casserole with spinach, sausage, cheese, and peppers.

What to Serve With Breakfast Casserole

For side dishes, fresh fruit and yogurt are light, simple, and quick. However, if you’re entertaining—or if you have several hungry teenagers in your house—pair this breakfast casserole with:

Your brunch guests will be beyond satisfied. Yes, even the teenagers!

Print
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breakfast egg casserole with peppers, spinach, mushrooms, and cheese.

Easy Make-Ahead Breakfast Casserole

  • Author: Sally
  • Prep Time: 20 minutes
  • Cook Time: 45 minutes
  • Total Time: 1 hour, 30 minutes
  • Yield: serves 12 1x
  • Category: Breakfast
  • Method: Cooking
  • Cuisine: American

Description

This easy breakfast casserole is infinitely adaptable and you can find variations and suggestions in the recipe Notes below. The version written below with sausage, mushrooms, bell peppers, spinach, and cheddar cheese is generally the most popular with guests. You can assemble the entire dish and refrigerate for up to 24 hours before baking.


Ingredients

Scale
  • 4 cups (175g or 6 oz) cubes of crusty bread*
  • 1 teaspoon olive oil
  • 1 pound ground pork sausage, casings removed*
  • 1 teaspoon dried rosemary or Italian seasoning, optional
  • 1/2 medium onion, diced (115g or 3/4 cup)
  • 2 garlic cloves, minced
  • 2 cups (275g or 910 oz) diced bell peppers
  • 1 cup (100g or 3 oz) sliced mushrooms
  • 1 cup roughly chopped fresh spinach
  • 12 large eggs
  • 1/4 teaspoon salt
  • 1/8 teaspoon freshly ground black pepper
  • 2/3 cup (160ml) milk or half-and-half*
  • 1 cup (100g or 3.5 oz.) shredded cheddar cheese
  • optional garnish: green onion and/or chopped parsley

Instructions

  1. Grease a 9×13-inch or any 3–4-quart oven-safe dish. Arrange bread cubes in an even layer in bottom of pan.
  2. Heat olive oil in a large skillet over medium heat. Add sausage and rosemary/Italian seasoning, if using, and break up the sausage into bite-size pieces with a wooden spoon or rubber spatula as it begins to cook. Add the onion, garlic, peppers, mushrooms, and spinach and cook until everything has slightly softened and sausage is mostly cooked through, about 5–6 minutes.
  3. Remove sausage and vegetable mixture from heat and spread in an even layer on top of bread.
  4. Whisk the eggs, salt, pepper, milk, and cheese together. Evenly pour over sausage/vegetable mixture. Add another sprinkle of salt and pepper on top.
  5. Cover casserole with plastic wrap or aluminum foil and refrigerate for at least 30 minutes and up to 24 hours. (When ready to bake, allow to sit at room temperature for 10–15 minutes as oven preheats.)
  6. Preheat the oven to 375°F (191°C). Bake the casserole, uncovered, until the top is golden, edges are crisp, and a toothpick inserted in the center comes out clean, about 40–45 minutes.
  7. Cool for 10 minutes, then slice and serve.
  8. Leftovers keep well in the refrigerator for up to 5 days. Reheat in the microwave to your liking.

Notes

  1. Make Ahead Instructions: This is an excellent make-ahead recipe because you can assemble it before baking up to 24 hours in advance. See step 5. You can also cook the sausage and vegetable mixture up to 24 hours in advance, cover and refrigerate until ready to use.
  2. Freezing & Reheating Instructions: To freeze, prepare and assemble through step 5, cover with plastic wrap, then a layer of aluminum foil, and freeze for up to 3 months. Thaw overnight in the refrigerator, and then bring to room temperature before baking as directed. You can also freeze the baked casserole for up to 3 months and when doing that, I suggest baking it in a disposable aluminum pan. Cool completely, cover with plastic wrap, then a layer of aluminum foil. When ready to eat, thaw it for about 24 hours (covered) in the refrigerator, remove the plastic wrap layer, then bake in a 350°F (177°C) oven for 25–30 minutes.
  3. Bread: Crusty sourdough is fantastic in this recipe, or use any crusty, hearty bread. The crustier or more stale, the better. If your bread is fresh and/or flimsy, cut into cubes and bake on a baking sheet in a 300°F (149°C) oven for 10 minutes. It’ll be slightly crisp and ready to use in this recipe. No need to wait for the bread to cool before layering into the baking dish.
  4. Using Potatoes Instead of Bread: You can replace the bread with diced hash brown potatoes—the kind you find in the freezer section of the grocery store. Use about 3 cups (around 380g) of frozen hash brown potatoes, no need to thaw. You could also peel and dice fresh potatoes, but you’ll need to quickly cook/brown them on a skillet with 1 Tablespoon olive oil over medium heat for 10 minutes before using.
  5. Sausage or Other Meat: If using pre-cooked sausage links or ham, cut into slices/chunks, and there is no need to cook either. Simply stir into the pre-cooked vegetables before layering into the dish. You can replace the sausage with ground turkey, beef, or chicken—simply pre-cook with the vegetables according to the instructions. If using bacon, I recommend reducing to 1/2 pound and cutting into bite-size pieces. Cook separately from the vegetables until browned. Drain, then mix with the vegetables before layering into the dish.
  6. Other Vegetables: Feel free to replace all or some of the bell peppers, mushrooms, and spinach with other vegetables such as chopped broccoli, sliced zucchini or squash, or kale. Pre-cook as directed.
  7. Vegetarian Option: You can leave out the meat and replace with another 1 cup of vegetables.
  8. Milk: For the richest, heartiest texture, I recommend half-and-half or whole milk. You can use lower-fat milk or dairy-free milk if desired.
  9. Cheese: I usually use a blend of regular and sharp white cheddar cheeses. Use whatever cheeses you like best, such as pepper jack, feta cheese, Swiss, and/or smoked gouda.
  10. Half Recipe: You can halve this recipe by halving all of the ingredients and using a 9×9-inch square pan. Bake time is slightly shorter, about 32–36 minutes.

Keywords: breakfast casserole, overnight breakfast casserole

Reader Questions and Reviews

  1. Easy great recipe. Enjoyed by all. Would do it again! I added a TSP of maple syrup to the sausage and only used veg on hand which was red/green peppers and yellow/green onion. Definately add the rosemary and I assembled the night before for brunch the next day. Great!

  2. This is my favorite egg bake recipe. I make it every year for Easter.

  3. Thankfully, there are plenty of plant based sausage substitutes that can be used to pump up the sausage flavor without the meat. I like Beyond Meat hot Italian flavor. Casings can easily be removed and cooked up as if you were using an animal product. This is fabulous and my (non-vegetarian) husband doesn’t know the difference! Yummer-rama!!

  4. This tastes wonderful, it is healthy and easy. Thank you, Sally. I have been making this without the bread in the bottom before, either in muffin pans or in ramekins that makes a bigger portion for my “hollow” husband.
    He loves bacon, so I can make this with so many variations, that it is always a plus to have it on hand. I calculate 6 eggs with 80ml of HWC/almond milk or whatever I have.
    I am truly blessed by your knowledge and good recipes!

  5. I need to prepare this in smaller 8 x 8 dishes to feed 3 people. Question 1: How long should i cook it if made last night?
    Question 2 : I also plan to freeze some, unbaked, so how long to cook if thawed overnight in fridge?

    1. Hi Sheila, you can halve this recipe for the 8-inch square pan. I’m unsure of the exact bake time, but I’m guessing around 30 minutes, however that depends on all the add-ins. Keep a close eye on it. Even after thawing, the bake time should be similar.

  6. Hi there
    My boyfriend and I are keen to try this recipe but we usually do a “meal prep” on a Sunday.
    Is it possible for us to cook this on Sunday, and slice a portion throughout the next 2 – 3 days to be reheated for breakfast? Or is reheating not a good option?

    1. Yes! Leftovers keep well in the refrigerator for up to 5 days. Reheat in the microwave to your liking.

  7. The recipe looks fantastic. I just made this for my parents. I split it into two 8″ square baking dishes, wrapped it in plastic and foil, and put it in the freezer. I will be delivering the casseroles to them this weekend. I can’t wait for them to tell me how it is! Thank you!

    1. Some readers have substituted the bread for potatoes with no problem. 2 cups should be plenty.

  8. This is one of the best breakfast casseroles! My whole family loves it!

    1. Hi Arina, We don’t usually include nutrition information as it can vary between different brands of the same ingredients. Plus, many recipes have ingredient substitutions or optional ingredients listed. However, there are many handy online calculators where you can plug in and customize your exact ingredients/brands. Readers have found this one especially helpful: https://recipes.sparkpeople.com/recipe-calculator.asp

  9. I had friends stop by unexpected for overnight. I plan to have this ready in the freezer if this happens again. Thank you for this recipe!!

  10. Can you do this at 350? if so for how long does it need to be in the oven?

    1. Hi Erin, you can bake this at 350 degrees if needed. We’re unsure of the exact bake time, but it will take bit longer. Keep an eye on it and bake until the top is golden, edges are crisp, and a toothpick inserted in the center comes out clean.

    1. Hi Deanna, We don’t recommend it. You’ll want to let it sit in the refrigerator overnight instead to give the bread a chance to soak up all of the eggs before baking.

    1. Hi Nita, we freeze the unbaked casserole. Prepare through step 5, then freeze. See recipe notes for more freezing / make ahead details.

  11. Haven’t tried it yet, but always looking for healthy and easy breakfast items for my twin boys. This has promise. Make in muffin tins, can actually add a variety to the main batter that way since my boys like different things. Bread in some, potatoes in others, etc. Ham and Swiss or feta and spinach…(Of course they can’t be easy.) Freeze cooked “muffins” and place in large ziploc bag. I think this would work, thoughts?

    1. Hi Holly, we don’t see why not! Let us know if you give it a try.

  12. Can this be baked, cooled and then cut into individual servings to be frozen and eaten days later?

  13. Would like to make the casserole ahead then freeze it then a couple days later microwave to eat it. How would I go about doing this?

    1. Hi Mary! For optimal texture and taste, the best way to make this casserole ahead of time is to follow the recipe instructions. You could certainly try baking the casserole, then freezing individual pieces to reheat later in the microwave (the whole casserole wouldn’t reheat well in the microwave). Make sure to completely cool the casserole before freezing. Let us know what you try!

  14. If I use dried bread pieces, will they soften enough with everything piled on top?

  15. If I cut this recipe in half, would I use an 8” or 9” square pan? There’s just 2 of us and I think 12 servings would be a bit much 🙂

  16. Hi Gwen! Some readers have substituted the bread for potatoes with no problem. 2 cups should be plenty.

  17. I would like to substitute hash brown potatoes for the bread. Can I still freeze this with hash browns?

  18. This is delightful! I make it a few times a year and my family loves it, thank you!!

  19. I always make this recipe when cooking breakfast for my big visiting family. I add some veggies and up the milk/egg mixture, and use bacon instead of sausage. It’s a huge hit every time! Individual leftover pieces freeze great too.

    1. Hi Ruby, we haven’t tested that but let us know if you do – sounds delicious 🙂

  20. I make a casserole similar to this, but use big croutons in place of the bread. Everyone loves it 🙂

  21. Hi! I will need this for an early morning event. Should I bake it up the night before and reheat the morning of OR bake it early and let it come to room temp in the oven while the oven is heating? I don’t know if it will dry out. Thank you!

    1. Hi Vera, you can actually do either! It’s a very forgiving recipe, and it’s great leftover. If you bake it the night before, you should let it cool a while at room temperature before refrigerating, so just make sure you have time for that. Enjoy!

  22. Hi- Do you think this casserole can be made a week ahead of time, frozen, then thawed and baked?
    It looks delicious!

    1. Hi Ann, absolutely! Prepare through step 5, then cover the casserole with plastic wrap, then a layer of aluminum foil. Freeze for up to 3 months. Allow to thaw overnight in the refrigerator. Bring to room temperature, then continue with step 7.

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