Overnight Breakfast Casserole for Easy Mornings

There’s nothing better than starting the day with a warm, comforting Breakfast Casserole. I love making this kind of breakfast when I want something hearty, satisfying, and easy to share with everyone at the table. With its savory flavors and cozy baked texture, it is perfect for slow weekend mornings, family breakfasts, or holiday gatherings. It can also be prepared ahead, making busy mornings a little easier. Serve it fresh from the oven with your favorite breakfast sides, and you have a delicious homemade meal that everyone can enjoy.

Why You’ll Love This Recipe

• Sleep in: You assemble the casserole the night before, so morning-you can hit snooze while it bakes.
• Clear out the fridge: You can add leftover spinach, peppers, mushrooms, and onions.
• Feed a group: This breakfast casserole for a crowd replaces endless individual omelets.
• Forgiving texture: Slight changes in the bread-to-egg ratio still create a hot, cheesy breakfast.
• Holiday-friendly: You can assemble everything on Christmas Eve and bake it the next morning.

Tools You’ll Need

Nothing fancy, I promise.

• 9×13 baking dish: Glass or ceramic works well if the dish fits your refrigerator.
• Large skillet: The skillet browns the sausage and cooks down the vegetables.
• Whisk: A whisk mixes twelve eggs without exhausting your arm.
• Rubber spatula: A spatula scrapes the skillet and spreads the filling evenly.

Ingredients

• 4 cups cubes of crusty bread – Stale is better. If it is fresh, toast it a bit.
• 1 teaspoon olive oil – Just to get the pan going.
• 1 pound ground pork sausage – If you want an easy make ahead breakfast casserole with eggs and bacon instead, just swap this for half a pound of cooked, chopped bacon.
• 1 teaspoon dried rosemary or Italian seasoning – Optional, but makes it smell fancy.
• 3/4 cup chopped yellow onion – About half a large onion.
• 2 garlic cloves – Measure this with your heart.
• 2 cups chopped bell peppers – Whatever colors were on sale.
• 1 cup sliced mushrooms – Wipe them clean, do not soak them.
• 1 cup roughly chopped fresh spinach – It looks like a lot, but it shrinks to nothing.
• 12 large eggs – The glue that holds this whole operation together.
• 1/4 teaspoon salt & 1/8 teaspoon black pepper – Plus a little extra for the top.
• 2/3 cup milk or half-and-half – Whole milk is best, skim milk makes it sad.
• 1 cup shredded cheddar cheese – Grate it yourself if you have the energy, but I will not judge the bagged stuff.
• green onion and/or chopped parsley – For garnish, if you are trying to impress someone.

How To Make Breakfast Casserole

Set it, walk away, and pretend you did not just outsource morning prep to your refrigerator.

1. Prep the pan: Grease your baking dish and arrange the bread cubes on the bottom. Missing a few spots is fine, the eggs will find their way to the bottom regardless.
2. Cook the meat and veg: Heat the oil, brown the sausage with the herbs, then toss in the onion, garlic, peppers, mushrooms, and spinach. If you accidentally burn the garlic slightly, just call it “roasted” and move on.
3. Layer it up: Spread the cooked sausage and vegetable mixture evenly over your bread cubes. Resist the urge to eat a spoonful of the filling right now, you need it for the casserole.
4. Whisk the eggs: Whisk the eggs, salt, pepper, milk, and cheese, then pour it over the pan. Give it a little shake to make sure the bread is completely drowned in cheese and egg.
5. Chill out: Cover and refrigerate for at least 30 minutes, or up to 24 hours. This is the crucial step for a prep ahead egg casserole for brunch, do not skip the resting time or you get dry bread.
6. Bake it: Bake uncovered at 375°F until the top is golden and the center is set. It will puff up like a majestic soufflé and then immediately deflate when you take it out, this is normal.
7. Cool and serve: Let it sit for 10 minutes before slicing. Cutting it straight out of the oven will result in a lava-hot mess, give it a minute.

Make It Yours

You can turn the sausage version into an egg bacon breakfast bake by replacing the sausage with cooked, chopped bacon. You can add shredded Monterey Jack or pepper jack for a different cheese flavor.

You can also add leftover roasted vegetables or chopped ham. The casserole welcomes substitutions as long as you cook watery vegetables before layering them.

Perfect Pairings

These go perfectly with anything you can pour into a mug.

• A giant vat of strong black coffee, obviously.
• Pre-cut fruit salad because you have boundaries.
• Mimosas when the overnight breakfast casserole recipe for Christmas morning needs festive support.
• Leftover holiday cookies because adults make the rules.
• Fresh orange juice for a bright contrast.

Breakfast Casserole

This make ahead breakfast casserole combines crusty bread, browned sausage, eggs, cheddar, spinach, peppers, mushrooms, and onions in one generous pan. You can turn it into an egg bacon breakfast bake with cooked bacon or assemble it as an overnight breakfast casserole for Christmas morning. The result gives you a reliable breakfast casserole for a crowd without early-morning stove duty. Prepare this easy make ahead breakfast casserole with eggs and bacon for brunch, holidays, or any morning that deserves more sleep.

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Prep Time 20 minutes mins

Cook Time 45 minutes mins

Total Time 1 hour hr 30 minutes mins

Servings: 12 servings

Course: Breakfast

Cuisine: American

Calories: 212

Ingredients Equipment Method Notes

Ingredients

  

• 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
• 3/4 cup (100g) chopped yellow onion (1/2 of a large onion)
• 2 g arlic cloves minced
• 2 cups (275g or 9-10 oz) chopped 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

Equipment

• 9×13 baking dish
• Large skillet
• Whisk
• Rubber spatula

Method

 

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.

Recipe Notes

Make Ahead:
Assemble the casserole up to 24 hours ahead and refrigerate before baking. The cooked sausage and vegetable mixture can also be prepared up to 24 hours ahead and refrigerated.

Freezing & Reheating:
Freeze the assembled, unbaked casserole for up to 3 months. Thaw overnight in the refrigerator, bring to room temperature, and bake as directed. You can also freeze the baked casserole for up to 3 months. Thaw covered for about 24 hours, remove the plastic wrap, and bake at 350°F (177°C) for 25–30 minutes.

Bread:
Use crusty sourdough or another hearty bread. If using fresh bread, cube it and bake at 300°F (149°C) for 10 minutes to dry it slightly.

Potato Option:
Replace the bread with about 3 cups (380g) frozen diced hash browns. No thawing is needed. Fresh diced potatoes should be cooked in 1 tablespoon olive oil for about 10 minutes before using.

Meat:
Use sausage, ham, ground turkey, beef, or chicken. Pre-cooked meats only need to be chopped and added to the vegetables. For bacon, use 1/2 pound, cook separately, drain, and combine with the vegetables.

Vegetables:
Replace the peppers, mushrooms, or spinach with broccoli, zucchini, squash, or kale. Cook the vegetables before layering.

Vegetarian Option:
Omit the meat and add 1 extra cup of vegetables.

Milk & Cheese:
Half-and-half or whole milk gives the richest texture, but lower-fat or dairy-free milk works. Use your favorite cheese or a blend, such as cheddar, pepper jack, feta, Swiss, or smoked gouda.

Half Recipe:
Halve all ingredients and bake in a 9×9-inch pan for about 32–36 minutes.