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

228 Comments

  1. Hello, thls sounds awesome. This might be a silly question, sorry if it is but I’ve never made a casserole. Does it have to be prepped overnight? What if I just want to make the whole thing in the morning for my family? I’m asking because I don’t know if letting it sit in the fridge over night does something extra for the flavoring. 

    1. Step 6 should be helpful– you can cover it and keep it in the fridge for 2 hours – overnight. Letting it sit for sometime, even 2 hours, allows to egg to soak into the bread and the flavors to blend.

  2. Hi!!
    Can I prepare this ahead Friday to cook Sunday am. And should I leave out the egg mixture until Sunday morning or should I commit all ahead and just warm it up??  

    1. Did you get an answer on letting it sit for two days? I prepared mine this morning and want to serve it the day after tomorrow. Do I have to freeze it until tomorrow night or can I let it sit in fridge for two days?

  3. 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!!

  4. This looks absolutely delicious, Sally! I love that you used so many different veggies. This makes it look so colorful and pretty. 🙂 

    I really want to make this soon! I’m vegan, so I’ll just leave out the sausage and replace the eggs with a mixture of silken tofu, turmeric and kala namak. I did that with a hash brown casserole a couple of weeks ago and it turned out really well (http://veganheaven.org/recipe/vegetarian-breakfast-casserole/). Thanks so much for sharing this!! I seriously can’t wait to give it a try soon. 🙂 

    Sina 

  5. If I replace bread with hash browns, how much would you recommend? Also, do I still need to let it set over night?

    1. I don’t, but here is a website I’ve used in the past to calculate. https://recipes.sparkpeople.com/recipe-calculator.asp

  6. Love this! Great that you can make ahead! And great that you can freeze! Perfect for making ahead and freezing portions for rushed mornings when you still want something hot! Thanks!

  7. Kind of giggling at myself for making this.  I had some leftover “veggies” and also a renewed determination to feed ’em healthy before sending off to school and work.  So, celery that was starting to go limp, extra green onions from another recipe, cherry tomatoes that were starting to take the term “ripe” to “really gross”, fresh arugula, and sautéed that in extra garlic.   I used the crusts from some sprouted grain bread and leftover chicken maple sausage links. Viola! Everyone loved it – this from 2 kids who think the only acceptable way to eat tomatoes is in ketchup and maybe salsa.  I mean, it looked good, but I thought I’d hear something about at least one of the veggies I put in there.
    I’ve made egg bakes before so why is this one so good?  I don’t think it was the celery 🙂  I’m wondering if it was the bread?  I will remain baffled and will make this very adaptable recipe again.  I really like having another option for my bread crusts.  That bread is so good!

    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.

  8. The question about whether you can used frozen hash browns instead of bread has been asked before, but has anyone actually tried it? Did you like it as well as with the bread?

  9. 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.

      1. I’m low-carbing it…looking for recipes that I can freeze. So glad someone asked about leaving out the bread! I’m going to give it a try, it sounds yummy!

  10. How long does it take to come to room temperature after being in refrigerator over night ?  Thanks. Looking forward to bringing this festive egg casserole  to the table. 

  11. Can this be re-heated in a microwave or does it have to go back in the oven?

    Would love to take a portion to work but we only have microwaves!!! Thanks

  12. I want to make this for a group of 4 people this weekend. If I cut the recipe in half do you think it’ll make a difference?

  13. The traditional name for this breakfast casserole is “Strata.”  My mother made this for holiday brunches for many years and I used to make it on the last morning of camping trips with 20 or 30 friends, using cast iron Dutch ovens in the fire pit while everyone was packing up camp to leave.  It was always a great way to use up leftovers – bread, veggies, milk, eggs and breakfast meats.  It was different every time and everyone always loved it, plus they loved the fact that they didn’t have to worry about cooking breakfast because someone else was doing it.  I would walk through camp, collecting everyone’s ingredients, then make two or three different versions since some folks wouldn’t eat onions or mushrooms or whatever.  It was also a great way to avoid wasting food since there was always leftover bread and milk that just weren’t going to survive the trip home. 
    Try it with bacon, ham, Kielbasa, Canadian bacon.  Using the Dutch oven makes it easy, layer in the bread, pour the egg, milk, meat, cheese & veggie mixture, then put the lid on, put it on some hot coals and lay some more hot coals on top, then leave it alone for 45 minutes or so, or until the top coals turn to ash.  Brush off the ash, lift the lid and check it for doneness and, if the eggs aren’t quite set, replace the lid and put on some more hot coals for another 15 minutes or so.  It is really hard to mess up a recipe in cast iron, especially when using coals in a fire pit.  And it tastes sooo good with good friends who need a break from hard work.  🙂

  14. Hi.  Sounds like such a great recipe!  I am making three pans of this for an early brunch at work.  I have to cook three of them at the same time.  Will I need to bake longer?  If so, any ideas about how long?
    Thanks.

    1. I would bake longer, yes. I can’t tell you the exact time, but they’ll be done when they’re nice and toasty on top and the centers are completely set.

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