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.

breakfast casserole in a glass baking dish

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.

breakfast casserole

↑ ↑ 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.

Print
clock clock iconcutlery cutlery iconflag flag iconfolder folder iconinstagram instagram iconpinterest pinterest iconfacebook facebook iconprint print iconsquares squares iconheart heart iconheart solid heart solid icon
breakfast casserole in a glass baking dish

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.

sautéed vegetables in a skillet with a wood spoon

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!

cooked sausage and rosemary in a skillet with a wood spoon

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.

2 images of cubed bread and whisked eggs in a glass bowl

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!

pouring egg mixture into glass casserole dish filled with vegetables and sausage

overhead image of pieces of breakfast casserole on green and yellow plates with a fork

101 Comments

  1. Looks great! A couple questions:
    Do you bake the casserole directly after removing it from the fridge or do you let it come to room temperature before placing it in the oven to decrease the chances of the glass shattering/cracking? If so, how long do you need to let it sit at room temperature for before you can bake it?
    Also, if you are making this vegetarian-friendly, how much extra vegetables would you recommend using in place of the meat? 
    Thanks!

    1. Rella– two great questions. Yes, let it come to room temperature before baking if it has been in the fridge. Add another cup or so of veggies.

  2. I made this today for a moms group and it was sooo good!!! Everyone enjoyed it and I will definitely be making it again soon! It had so much flavor, like all your recipes! Thanks for the hard work and great recipes!! I am making you French toast casserole for breakfast tomorrow. It is delicious as well!

  3. I just made the vegetarian version. I halved the recipe & used a deep pie dish. I also used rice milk. It was great!

  4. Hi Sally – love your recipes! Is it necessary to make this ahead and refrigerate, or can one assemble it and cook it immediately? Thanks! 

    1. Let it sit for at least 2 hours before baking. (see step 6) So the bread can really soak up some moisture… which creates incredible texture in the final dish.

  5. I just made the casserole it’s in the refrigerator looking forward to baking it in the oven tomorrow morning.   I’m bringing it into the office for our Thanksgiving breakfast 

  6. Sally, this looks delicious.  I’d love to make it for Christmas morning.  My daughter in law does not like ore eat cheese.  Any ideas?

    1. You can leave out the cheese, no problem!

  7. Thanks for a great recipe and an EXTRA THANK YOU for your format. So many bloggers show all the step-by-step directions FIRST so to actually get the recipe you have to scroll, scroll and scroll, then scroll some more.  I push my computer to the max with tons of tabs so sometimes it gets bogged down with scrolling! I SO APPRECIATE you giving the recipe first then the step-by-step directions for those who need them. 

  8. culinarykitten says:

    Thank you for a wonderful recipe! I’m a huge frittata fan, and typically make them using roasted vegetables, fresh herbs and whatever cheese and meat I have on hand. However, adding the bread layer takes it to an entirely new level – it’s like a beautiful, savory bread pudding, chewy and custard-like.. I loved being able to assemble it ahead of time and pop it into the oven to let it bake while I enjoyed coffee..

    I made this for Christmas morning brunch using roasted zucchini, cherry tomatoes, yellow, orange and red bell peppers, garlic and shallots, rosemary and tarragon with Gruyere, Parmesan and a little prosciutto. Everyone raved! Will be making this again and again..

  9. Made this for Christmas morning and it was a big hit. I couldn’t get enough, myself. Trying it again today. Saw another recipe where they cut up can biscuits, cut up on the bottom. Going to try it. Also didn’t make it ahead so I’m hoping it won’t be a problem. Love this recipe. Thanks for sharing and Happy Anniversary and New Year. 🙂

  10. Did you mention somewhere that this can be frozen AFTER it’s baked? I don’t have room for a baking pan in my freezer but I do have room for smaller portions after its baked.

    1. Yes, I’ve done it before! Simply let it thaw overnight in the fridge then heat in a 350 oven until warmed through. 20 minutes or so.

  11. I made this casserole last night. Let it sit in the fridge for two hours, omitted the meat and substituted an extra 8oz of mushrooms. It’s delicious!!! I will be reheating it in the oven so it can crisp up again. Awesome flavor.

  12. Hi Sally! I’m having company for breakfast on Saturday and know this will be a hit (as all of your recipes always are!) but wondered about timing.  Do you think I could assemble it on Friday morning, refrigerate until Saturday morning and then bake or would that be too long for it to sit?
    [I’m really just trying to sleep for as long as possible on Saturday morning 😉 ]

    1. That long is OK to sit in the fridge– I’ve done it before a few times!

  13. Hi Sally- my daughter and I love your blog and recipes! Can this be eaten at room temp or is it better warm out of the oven? Thank you dally!

    1. I love it room temp– even cold sometimes! The flavor is best at room temp in my opinion.

  14. Made this for Easter brunch. I left out the sausage and added asparagus. It was super easy to make and so good!

  15. If I am making this to freeze divided into two 8×8 pans what should my cook time for them be once thawed?

    1. About 30 minutes, maybe a bit longer.

  16. My husband calls this “breakfast fiesta” and insists I make it when we have company. My mom even asked me for the recipe. My mom… Asked me… How to make something. We leave out the mushrooms, and I swapped the yellow onions for chopped green onions, but, needless to say, this reside is a huge hit in my house. Thank you!!!

  17. This was SO easy and I enjoyed all the add-ins exactly as you recommended!  Love that I was able to just stick it in the oven in the morning.

  18. This looks and sounds soo yummy! I am really trying to stay away frim bread, can i make this with out bread? Or what shuld i sub it with? Thanks

    1. The casserole won’t have that chewy texture and more satisfying flavor, but you can absolutely leave out the bread to make a lighter texture-d (and calorie!) casserole.

  19. Christie Knott says:

    Can you substitute bacon for the sausage?

    1. Absolutely!

  20. Made this a few weeks ago and it was AMAZING!!!

  21. This is a magnificent recipe!!  I subbed bacon (cooked and crumbled into veggies after sautéing) and used 8 oz of shredded pepper jack vs 1/2 c.  My casserole dish was bigger than 13×9, so used 6 slices of gluten-free bread, cubed. Will absolutely make again!!

  22. Can’t wait to try this out! I was wondering if instead of bread, using small fingerling potatoes? 

    1. Yes, definitely! I’ve had a few readers ask about that– and some have tried it too.

  23. Made this last night and had for dinner tonight. My hubby and I LOVED IT. We both had seconds. Will definitely be making again.

  24. What kind of sausage do you find works best – mild Italian?

    1. I’ve made the casserole with several different kinds actually– italian sweet, mild italian, breakfast sausage, smoked sausage– it’s all so good! You can’t go wrong. Just use what you like best.

  25. I have made a breakfast casserole like this for year but always used seasoned croutons instead of bread; really makes it full of flavor. But if I need to make it without bread of any kind what can I use as a binder that would work like bread but without the carbs?

    1. Hi Deborah, you can simply leave the bread out in this particular casserole. The texture of the casserole will change, but it will still have wonderful flavor.

  26. Adelita Campbell says:

    Made this the day before Easter and it was a hit!! I let it cook a little bit longer as I added extra eggs and veggies and sausage, came out perfect. Thanks!

  27. Have you tried baking this and then freezing it in individual serving sizes? It looks AMAZING!

    1. I personally haven’t but it should work pretty easily!

  28. Do you drain the grease after you brown the sausage?? Thanks! 

    1. I don’t!

  29. Have you ever added hash browns to this recipe? How can I incorporate them-my family loves them in egg casseroles.

    1. I’ve had readers replace the bread with frozen hash browns. Yum!

  30. I noticed you said you’ve used broccoli before.. did you boil it first or just heat it up in the skillet? Excited to try it! Making it with broccoli, spinach, onion and kielbasa!

    1. Hi Liz! I actually boil it first. Helps cook it down a little before baking in the casserole.

1 2 3

Leave a Reply

Your email address will not be published. Required fields are marked *

Recipe rating

This site uses Akismet to reduce spam. Learn how your comment data is processed.

With kitchen-tested quality recipes and step-by-step tutorials, my goal is to give you the confidence to bake and cook from scratch.

Sally's signature

Recipes You’ll Love

Archives

Categories

Join the community on the 1st of every month as we tackle a new challenge recipe. Review Sally's Baking Challenge FAQ page if you have any questions.

View More

A tradition since 2013, every December we countdown to Christmas with 10 new cookie recipes in a row!

View More

The first week of every November is all about Thanksgiving Pies.

View More

My Cookbooks

Sally's Cookbooks

About Sally

Welcome to my Kitchen!

I’m Sally, a cookbook author, photographer, and blogger. My goal is to give you the confidence and knowledge to cook and bake from scratch while providing quality recipes and plenty of pictures. Grab a cookie, take a seat, and have fun exploring! more about Sally

×