Sourdough Breakfast Casserole

I bake a lot of sourdough bread, and sometimes I have a loaf or two that gets left on the counter for a little too long and starts to dry out. When that happens, I often cut the bread up into pieces and stick it in the freezer to make croutons, but something else I love to do is use them to make this incredible sourdough breakfast casserole. This sourdough breakfast casserole is easy to throw together and the perfect dish to serve at a weekend brunch or special occasion. I am a sucker for a good breakfast casserole, and this one hits all the right notes – sausage, egg, cheese, sautéed vegetables and of course, sourdough bread.

Why You’ll Love This Sourdough Breakfast Casserole

You will love this sourdough breakfast casserole because you can make it ahead of time or the day of. As long as the egg mixture soaks the bread for at least an hour (or overnight), you are good to go. This casserole will save you time, it tastes delicious and feeds a crowd. Using your homemade sourdough bread only makes it taste better. This casserole is also adaptable to whatever ingredients you have on hand in your fridge that you need to use up. It’s seriously delicious!

Important Ingredients in Sourdough Breakfast Casserole

  • Sourdough Bread: This recipe calls for about 8 cups or half a loaf of sourdough bread cubed. Use crusty stale bread or bread that has been sitting around for a day or two for best results.
  • Bell Peppers: I love a combination of red, yellow and orange sweet bell peppers in this casserole. Use whatever peppers you like.
  • Sweet Onion: Onion gives a delicious flavor when sautéed. Use a small/medium onion or half of a large onion.
  • 1 lb Breakfast Sausage: I love the flavor of ground breakfast sausage. Cook it in a frying pan and drain the grease before adding to the casserole.
  • Eggs: This casserole is an “eggy” dish. The eggs bind together the bread at the bottom and turn them custardy and yummy – almost like a savory bread pudding.
  • Whole Milk: Whole milk is added to the eggs to soften the bread cubes and add moisture. 2% milk works too.
  • Gruyere Cheese: Gruyere cheese is my favorite – though any good quality cheese will work. Shred it before sprinkling on top of the casserole.
  • Parmesan Cheese: Parmesan adds a nutty flavor to the casserole that I love. Shredding it yourself is preferred, but if you have a pre-shredded Parmesan that you like, you can use that too.
  • Garlic Cloves: Minced garlic is sautéed with the vegetables, adding to the overall flavor of this dish. 1 teaspoon garlic powder could be added into the milk mixture in a pinch.
  • Salt: Salt the vegetables as they are being sautéed, sampling and making sure they have the right flavor before adding them to the casserole. This helps build layers of flavor in the dish.
  • Pepper: Just a little bit of ground black pepper adds flavor and depth to this casserole.
  • Mustard Powder: Mustard powder enhances and adds flavor to the casserole. You can substitute it for a teaspoon of Dijon or yellow mustard instead if desired.

How to Make Sourdough Breakfast Casserole

Cube the Bread, Cook Meat and Sauté Vegetables

Cube the bread and place it in the bottom of a buttered casserole dish. Cook the sausage over medium-heat in a frying pan until crumbled and cooked all the way through. Pour off the grease, reserving some to use to sauté the vegetables. Spread cooked sausage on top of the cubed bread. To the same frying pan, add some of the reserved grease and sauté vegetables until soft and tender. Layer vegetables on top of the casserole.

Add Cheese & Egg Mixture and Refrigerate

Spread grated cheese on top of the casserole. Whisk eggs, milk, mustard powder, salt and pepper together. Pour on top of the casserole. Cover with aluminium foil and stick in the refrigerator for 1 hour or up to 16 hours (overnight if that helps you!). The longer it sits, the more the egg mixture will soak into the bread, creating a custardy texture.

Bake and Enjoy

Pre-heat the oven to 350ºF. Once pre-heated, bake the breakfast casserole for 20 minutes with the foil on. Then take the foil off and finish baking for 30-35 minutes until bubbly, puffed up and baked all the way through. Let the casserole cool for about 5 minutes before slicing and serving. Enjoy!

Amy’s Recipe Tip

This is a great recipe for meal planning. You can make a big batch of this breakfast casserole and have it on hand throughout the week or freeze individual slices to heat up and enjoy when you need a quick breakfast.


Truthfully, many ingredients will taste delicious in this sourdough breakfast casserole. Don’t like peppers? Substitute mushrooms! Have spinach that needs to be used up? Add it to this casserole. Use what you have on hand or your favorite flavors to make it delicious.

  • Sausage – Substitute bacon for the sausage in this recipe or any other favorite breakfast meat. Or leave the meat out completely and add more vegetables for a vegetarian version.
  • Vegetables – Use any vegetables you like in this casserole. Before adding the vegetables in, chop or dice them and sauté in a little bit of olive oil until tender. Add in place of the vegetables in this casserole.
  • Cheese – Substitute any favorite cheese for the Gruyere cheese. Fontina, sharp cheddar, pepperjack or any other favorite cheese would work well.
  • Bread – I make my own sourdough bread for this recipe. I love this beginner sourdough recipe or this more advanced sourdough recipe. If you don’t have homemade sourdough bread on hand you can use any crusty bread from the grocery store.

How to Store Leftover Sourdough Breakfast Casserole

Leftover sourdough breakfast casserole can be sliced and stuck in an airtight container and refrigerated for 5 days. After that, it should be frozen for best results. Refrigerated or frozen casserole can be re-heated in the microwave or warmed in the oven before serving.

If you liked sourdough breakfast casserole, you’ll also like…

Any sourdough recipe that is great for a gathering. I love serving these recipes at parties, brunches and to family and friends when we are visiting together.

Frequently Asked Questions

Can I make a smaller version of this sourdough casserole?

Yes. You can cut the recipe in half and bake in an 8 by 8 pan or cut it even smaller into fourths and bake in a loaf pan.

Why are the measurements for this casserole in cups (volume) instead of grams (weight)?

I find it easier when cooking to use volume or cup measurements instead of grams and weight. Cooking is easier to “eyeball” and has more room for error than baking recipes. All of my baking recipes you will find in grams, but cooking recipes will more likely be in cups with a few weight measurements as needed.

Can I make this breakfast casserole ahead of time?

Yes! This is a great casserole to make ahead of a big celebration or weekend brunch. Mix everything up the night before and stick in the refrigerator for 12-16 hours until you are ready to bake it. Bake and enjoy!

Do I have to use stale or old bread?

No. You don’t have to. I find this casserole to be a great use for stale bread, but you can also use a freshly baked loaf of bread – just make sure it’s cooled completely before cubing for the recipe.

Sourdough Breakfast Casserole

Sourdough breakfast casserole is the perfect recipe for a weekend brunch or delicious meal when you want to use up some day-old sourdough bread. Savory and packed full of delicious breakfast flavors, this sourdough breakfast casserole is full of sourdough bread, eggs, vegetables, cheese and breakfast sausage. It's filling and absolutely delicious – perfect for a sourdough baker to serve to a crowd!
5 from 2 votes
Prep Time 30 minutes
Cook Time 55 minutes
Refrigerated Rest 1 hour
Total Time 2 hours 25 minutes
Course Breakfast
Cuisine American
Servings 1 9 by 13 casserole



  • 8 cups cubed sourdough bread about 500 grams
  • 1 lb breakfast sausage
  • 2 bell peppers chopped (red, yellow and orange peppers work best)
  • 1 sweet onion chopped or diced (small or medium size onion)
  • 3 cloves garlic, minced
  • 10 large eggs
  • 2 cups whole milk 2% also works well
  • 1 teaspoon mustard powder
  • 1 teaspoon salt
  • ½ teaspoon pepper
  • 1 cup Parmesan cheese shredded
  • 1 cup Gruyere cheese shredded, see recipe notes on cheese
  • 1-2 Tablespoons olive oil to sauté vegetables if needed
  • 1 Tablespoon unsalted butter, softened for the pan


  • Prepare a 9 by 13 casserole dish by buttering the pan. Add cubed sourdough bread to the buttered pan.
  • Cook 1 lb of breakfast sausage in a skillet over medium heat until browned and cooked all the way through. Reserve some of the grease to use in cooking the vegetables and pour cooked breakfast sausage evenly over the cubed sourdough bread.
  • While the sausage is cooking, prepare the vegetables by slicing and dicing peppers, onion and garlic. Pour a little of the grease from the sausage into the same frying pan and sauté peppers and onions over medium-low heat for about 5-10 minutes until softened. Add the garlic and a pinch of salt and pepper to the pan and sauté another few minutes until fragrant. Pour the vegetables on top of the sausage in the casserole dish.
  • Shred the Gruyere and Parmesan cheeses and sprinkle on top of the vegetables, covering the entire casserole dish.
  • To a medium-sized bowl, whisk together eggs, milk, mustard powder, salt and pepper until combined. Pour evenly over the top of the casserole. Cover with aluminium foil and stick in the refrigerator for one hour or overnight (12-16 hours).
  • Before baking the breakfast casserole, pre-heat the oven to 350ºF. Place the casserole in the oven and bake for 20 minutes with the aluminum foil covering the casserole. After 20 minutes, take the cover off the casserole and bake for another 30-35 minutes until puffed up, browned and baked all the way through. Let cool for about 5 minutes and serve. Enjoy!


Cheese: We love this sourdough breakfast casserole with Gruyere cheese, but you can substitute any cheese that you prefer. Other good options: fontina, sharp cheddar, pepperjack or any favorite cheese.
Variations: You can add any vegetables you like to this sourdough breakfast casserole. I like adding mushrooms, spinach and even tomatoes. 1-2 cups more of sautéed vegetables can be added that have been cooked down or you can replace the vegetables in this casserole with ones that you prefer.
Sourdough Bread: This is the recipe I use for my sourdough bread. Whatever bread you choose to use, the bread should be completely cooled. I prefer using bread that is a day or two old in this recipe. 
Keyword holiday breakfast casserole, make ahead sourdough breakfast, sourdough breakfast casserole, sourdough breakfast strata, sourdough egg casserole
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