Easy Make-Ahead Breakfast Casserole

This easy breakfast casserole is infinitely adaptable! Use your favorite seasonings, vegetables, meats, cheeses, or make it vegetarian. The best part is that you can prepare it ahead of time so breakfast is a breeze in the morning.

Easy breakfast casserole you can freeze or make the night before! Use your favorite vegetables, meats, and cheese. Recipe on sallysbakingaddiction.com

Today’s breakfast casserole recipe comes from my dear friend Kristen. She made it for us when we visited last month. As I gobbled it down, I couldn’t stop saying “I have to share this on my blog, I have to share this on my blog, I have share this on my blog.”

As it turns out, this is something Kristen makes on the regular. And I understand why! Besides taste, this breakfast casserole is pretty impressive in the health category. Full of protein, packed with vegetables. Not only that, it’s so easy to make and adaptable to whatever veggies, cheeses, meats, seasonings you love/have on hand. Confession. I’ve made this 4 times in 3 weeks.

Easy breakfast casserole you can freeze or make the night before! Use your favorite vegetables, meats, and cheese. Recipe on sallysbakingaddiction.com

↑ ↑ Soooo much texture and flavor!

This is a big breakfast casserole. I’m talking 12 huge servings, so it’s perfect for dinner or breakfast/lunch the next day. I reheat it in the microwave and top it with hot sauce. Delicious! I took a bunch of step-by-step photos so instead of displaying them all above the recipe, I included them below along with more detailed instructions for you.

Entertaining? If you’re entertaining, pair this breakfast casserole with slow cooker cinnamon rolls or my overnight cinnamon rolls. Both homemade and both VERY easy, especially if you’re a yeast beginner.

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Easy Make-Ahead Breakfast Casserole

  • Author: Sally
  • Prep Time: 8 hours, 35 minutes (overnight)
  • Cook Time: 40 minutes
  • Total Time: 9 hours, 20 minutes
  • Yield: serves 12
  • Category: Breakfast
  • Method: Cooking
  • Cuisine: American

Description

This easy breakfast casserole is infinitely adaptable! Use your favorite seasonings, vegetables, meats, cheeses, or make it vegetarian. Makes excellent leftovers for breakfast, lunch, and dinner during the week! Make sure to read the recipe notes and check out all the step-by-step pictures below this recipe before you begin.


Ingredients

  • 3/4 pound uncooked sausage, casings removed*
  • optional: 1 teaspoon dried rosemary to give the sausage more flavor
  • 2 bell peppers, diced (any color you prefer; about 2 cups)
  • 1 cup sliced mushrooms
  • 1 cup fresh spinach
  • 1/2 medium yellow onion, diced
  • 1 teaspoon minced garlic
  • salt and fresh ground black pepper
  • 4 slices day-old bread (gluten free, whole wheat, white, sourdough, any kind you like)
  • 10 large eggs
  • 1/2 cup milk (I use almond milk, any milk works)
  • 1/2 cup shredded cheese*

Instructions

  1. Set a large skillet over medium heat and coat it with nonstick spray or a drizzle of olive oil. Place sausage in the skillet and begin to break it up with a spatula or fork. Stir in the rosemary and brown the sausage, about 6-7 minutes.
  2. Meanwhile, set a 2nd skillet over medium heat and coat it with nonstick spray or a drizzle of olive oil. (If you have a skillet large enough to fit both the sausage and veggies, you can just add the veggies to the sausage that is browning in step 1.) Add the peppers, mushrooms, spinach, onion, garlic, and a sprinkle each of salt and pepper. Begin stirring and cooking the veggies down until tender, about 6-8 minutes.
  3. Set sausage and veggies aside.
  4. Generously grease a 9×13 baking pan. Break the bread into pieces and place in the pan in an even layer.
  5. In a large bowl, whisk the eggs, milk, and 1/4 cup shredded cheese together. Pour half of this egg mixture over the bread. Top with the sausage and vegetables, then the remaining egg mixture and remaining 1/4 cup cheese. Add a sprinkle of salt and pepper on top.
  6. Cover casserole with plastic wrap or aluminum foil and refrigerate for 2 hours or overnight– or up to 1 day. Allow it to come to room temperature before baking.
  7. 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. I like mine on the super crisp side, so I bake it for around 45-50 minutes. Allow to cool for 10 minutes, then slice and serve. Tastes awesome with hot sauce on top.
  8. Leftovers keep well in the refrigerator for up to 5 days. Reheat in the microwave to your liking.

Notes

  1. Make Ahead & Freezing Instructions: Obviously this is a make ahead recipe! However, you can brown the sausage and cook down the veggies up to 2 days in advance– simply put the two in a tupperware in the refrigerator until ready to use in the recipe. Also, you can freeze this breakfast casserole. 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.
  2. The onion, garlic, salt, pepper, and cheese are key to great flavor! Don’t leave them out.
  3. Sausage: Instead of sausage, try browning ground turkey, ground beef, or ground chicken instead. Or use ham. Or cooked shredded chicken.
  4. Vegetarian Option: You can leave out the meat. Just an extra cup (or so) of veggies in its place.
  5. Cheese: I usually use shredded pepper jack cheese– other varieties I love for this breakfast casserole are mozzarella, smoked gouda, swiss, and cheddar.
  6. Special Tools: Skillet | Glass Mixing Bowls | Whisk | Wooden Spoon | Glass 9×13 Baking Dish

Keywords: breakfast casserole, overnight breakfast casserole

How to Make Breakfast Casserole

Vegetables: Gather veggies like colorful peppers, mushrooms, and spinach. I’ve done this with broccoli/peppers, kale/mushrooms, and spinach/zucchini. Try to stick to 3-4 cups veggies total. Cook the veggies down with a little garlic, onion, salt, and pepper. Those last 4 ingredients are where all the flavor comes from.

Easy breakfast casserole you can freeze or make the night before! Use your favorite vegetables, meats, and cheese. Recipe on sallysbakingaddiction.com

Meat: We like a little meat in the casserole, so I add sausage. Kristen usually uses turkey sausage, so go ahead and use that if you prefer. Instead of sausage, try using ground turkey, ground beef, or ground chicken instead. You can also use diced pre-cooked ham or cooked shredded chicken. You don’t need to pre-cook either of those options.

I brown the sausage with some rosemary to give a little flavor. You can cook down the veggies and brown the sausage in 1 giant skillet if that’s easier for you.

  • Vegetarians: You can leave out the meat. Just use some more veggies in its place!

Easy breakfast casserole you can freeze or make the night before! Use your favorite vegetables, meats, and cheese. Recipe on sallysbakingaddiction.com

Bread: Grab your favorite crusty bread and tear it into little pieces. The bread will be the bottom of the casserole. It soaks up some of the egg and gives the egg casserole texture. It is SO good! Otherwise, you’d just be eating a quiche of sorts. I’ve been using gluten free bread for my sandwiches lately, so if you don’t eat gluten, you can use your favorite GF variety. Or you can certainly use wheat, sourdough, white, rye, whatever. You’ll need about 4 slices of bread.

Easy breakfast casserole you can freeze or make the night before! Use your favorite vegetables, meats, and cheese. Recipe on sallysbakingaddiction.com

Eggs, milk, & cheese: Whisk the eggs with a little milk and cheese. Like the veggies and meat, use whatever cheese you like best. I’ve been using pepper jack cheese for its flavor but I’ve done everything from cheddar to smoked gouda and swiss. Half of the egg mixture goes on top of the bread, then sausage and veggies, then the remaining egg mixture.

Once the eggs are poured on top of it all, you can refrigerate the casserole overnight. Wake up and all you have to do is throw it in the oven. When we visited Kristen, the morning was totally no-fuss; all she did was brew some coffee and cut up fresh fruit as the casserole cooked. Enjoy!

Easy breakfast casserole you can freeze or make the night before! Use your favorite vegetables, meats, and cheese. Recipe on sallysbakingaddiction.com

Easy breakfast casserole you can freeze or make the night before! Use your favorite vegetables, meats, and cheese. Recipe on sallysbakingaddiction.com

Easy breakfast casserole you can freeze or make the night before! Use your favorite vegetables, meats, and cheese. Recipe on sallysbakingaddiction.com
Easy breakfast casserole you can freeze or make the night before! Use your favorite vegetables, meats, and cheese. Recipe on sallysbakingaddiction.com

255 Comments

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  1. How much time will it take a 9 X 13 dish to come to room temp before cooking? Is an hour enough time?

  2. Looks delicious! Are there other veggies you think would work well in the casserole if I’m making this vegetarian?

    1. In addition to what is listed you can add kale, broccoli, zucchini, tomatoes, really anything you enjoy eating!

  3. Looks Great Sally – i made a copy of the recipe. I made a 6 inch cake today and frosting and took a couple of pics tomorrow – because i just got my internet and land line phone working after 2+days! Anyway it seems solved. Will send pics to you – email, reply to this tomorrow – anything , Its not great but its not too bad. Was nervous trying to go with the butter, eggs, cream, sugar and my Daddio 6inch pans and have been reading so much on the room temperature, and all of your wonderful explanation of base and acid or the ingredients. At&t had a real block out here in Wi. Not too happy about that. Thanks again for all of your knowledge!

  4. A little nervous about assembling and freezing ahead of time (without baking). I have a huge brunch to prepare for next weekend and would love to prep ahead of time. Have you ever done this method? Do you think it’s better to bake them freeze? TIA!

  5. Hi, I was wondering if it would be okay to fully prepare, portion out and then freeze? I would only be making this for myself so it would be nice for it to be all done and then only thaw a couple at a time to take on the go for breakfast. Can’t wait to try it.

  6. I want to make this ahead of time and freeze for a trip. Do I have to use a glass baking dish or can I use an aluminum throw away pan.

  7. I was looking to make this for a breakfast potluck at work. Can this be made in muffin tins for single servings?

    1. I think the flavor would be delicious! I’m unsure of how the texture of the chips would hold up but will you please let me know if you try – it sounds great!

  8. Hi Sally!
    My mom and I are considering making this for breakfast on the morning after Thanksgiving, but we were kind of confused about the bread at the bottom. Is it like a crust? What is the texture of the bread like after baking?
    Thanks!

    1. Hi Ricki! It’s not a crust– it helps soak up the egg so the casserole isn’t flimsy and liquid-y. It has a chewier texture. Definitely try it– it’s 100x better with a little bread!

    2. I’m looking forward to making this recipe! Does it need to come up to room temperature before baking it if it’s refrigerated in a Pyrex dish?

      1. It doesn’t, so it may take a few extra minutes if going into the oven cold. Doesn’t make a huge difference on bake time.

  9. Hi Sally, I make a very similar thing but do it in large muffin pan and use your piecrust as bottom and top…kind of mini pies. I sprinkle sage on top my kids’ spouses love these so it’s always a breakfast or anytime snack!

  10. Is it possible to omit the cheese? It seems to help in binding the casserole – do I need something instead of the cheese?

  11. Just wondering why you need to let the casserole come to groom temperature before baking? Could you not bake from fridge?
    Thank you.

    1. Hi Nancy! Placing a cold baking dish in a hot oven could warp it (or even shatter it). You can if you’d like to take that risk– sometimes I do with my ceramic pans– but it’s best to bring to room temperature first to avoid that possibility.

  12. 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!

  13. Thanks for the quick response! I’m going to try it this weekend. Leave the rosemary out then?

  14. Hi Sally! I don’t have a nonstick spray. Since I want to try this for the first time tomorrow, what can I grease the baking dish with? And then also I will buy one the next time I can. What nonstick spray do you recommend and use most in baking? Thank you! (So glad you showed this the other day in Stories! Will be my birthday brunch meal!)

    1. Hi Celine, I’m unsure of the nutritional info of this recipe, but there are many great online calculators like this one: https://recipes.sparkpeople.com/recipe-calculator.asp

  15. I suppose I should have asked this beforehand, but I needed to cook this yesterday as I let it sit out too long and got to room temp for too many hours. (Wish we had an emergency ‘Help’ line!) I halved the recipe for the smaller Pyrex square. I could only find medium eggs. So I used 6. But then it cooked too fast so it’s dry. And the eggs seem to have disappeared. So for next time, how many eggs would you recommend if we only have medium or small eggs? Thanks!

    1. Hi Elizabeth! If using medium eggs, I recommend around 12-13. If it’s dry, I wonder if the halved measurements were off or if the casserole was overcooked?

      1. Thank you so much for taking the time to reply! I’ve been taking notes as I try each new recipe. So I went back over my notes. I did use half the veggies and meat. The only things I used full amount as recipe is written are the cheese and garlic for more flavor. Since you said 12-13 eggs if using medium, the 6 eggs should’ve been sufficient. So I think I probably overcooked it. I checked at 30 minutes but it didn’t seem done, so I put it in for 10 more minutes. It got very brown on the bottom but didn’t burn (gas oven). So maybe next time I should just trust it’s done at 30 minutes? But this is such a great forgiving recipe. Thankfully it’s still edible!

  16. 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!!

  17. 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!

  18. I’ve just finished putting this all together to throw in the oven for tomorrow morning to find out we aren’t having Eid until Monday. So my question is will it be okay to sit in the fridge for two nights?

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