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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. Approximately how many cups of bread cubes do I need? I want to use Sourdough bread but the loaf is not large. I am uncertain if 4 slices will be enough. THANKS!!

  2. Made this last night and baked, this morning, for family. Thumbs up around the table. So easy and delicious.

    1. Could it be made without bread or potatoes for it to be keto friendly. Thank you

    1. Hi Vicki, if you are not using frozen hashbrown potatoes, I recommend a quick cook, yes. See specific details in the recipe Note.

  3. Great breakfast casserole! And, yes, you do need all those eggs! Thank you for sharing a version that doesn’t skimp on the eggs, Sally! I have made this with many leftover meats and veggies, and, added whatever cheese I have on hand, and it’s always delicious!

  4. Sally, this sounds wonderful, but can I halve the recipe.?My oven currently does not work, so I would have to use my KitchenAid toaster oven.
    Can’t wait to make this, as I am a vegetarian always looking for new recipes.

  5. I make a recipe really similar to this and use big croutons in place of the bread and it adds so much flavor!!

    1. I do the same. I use salad croutons, and bake in muffin tins instead of a pan. Freeze them for individual take along breakfast after warming in the microwave or toaster oven. I love to pack these when we leave in the early morning for a trip. We can eat on the road, with a travel mug of coffee or juice!

    2. I am definitely going to try this, thank you!
      I am wondering if you think it would be ok to use frozen spinach (thawed and water squeezed out) instead of fresh spinach?

      1. Hi NK, that should work, especially since the spinach will be sauteed with the other vegetables. Hope it’s a hit!

    1. Absolutely! I would use 2 cups of bread cubes and 1.5 cups of potatoes (so, half of each).

  6. I hosted my family for the first time in our new house and made breakfast for dinner using this recipe and Sally’s banana bread recipe. Both were HUGE hits! I will be making them again!

  7. Your recipe looks amazing! I know my family would love it. Unfortunately, I am not an egg person so am wondering if there is a way to substitute more heavy cream in lieu of some of those eggs? It would be more of a custardy type of casserole but not sure how that would affect your dish. Any thoughts?
    I love so many of your recipes, THANK YOU!!

  8. Made this for my 10 and 12 year old sons. They’re not crazy about lots of veggies. I made this with potatoes, red and yellow bell peppers, spinach and chopped broccoli and Italian sausage. They LOVED it! I made two batches, portioned into small squares and froze. This will make great breakfasts on busy mornings when we have to get out the door for school. Thanks for another great recipe that my family loves!

    1. So happy to hear that this breakfast casserole was a hit with your family, Kelli!

  9. This was perfect for serving my in-laws when they stayed over. I prepped it the evening before, then baked in the morning. Absolutely perfect!

  10. Hi Sally
    My family loves this recipe and I’ve made it several times. Can this casserole be made with egg whites for a lower cholesterol versions?
    Thank you
    Nancy

    1. Hi Nancy, We haven’t tested this recipe with only egg whites. We’re unsure of the exact amount that would be best – let us know if you try it!

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