Breakfast

Overnight Breakfast Casserole

Name: Overnight Breakfast Casserole
Prep time: 20 min
Cook time: 55 min
Total time: 9 h 15 min
Yield: 8 servings
Cuisine: American
Ingredients: 1 pound breakfast sausage, casings removed; 8 cups day old crusty bread, cut into 1 inch cubes; 1 small yellow onion, diced; 1 red bell pepper, diced; 2 cups shredded sharp cheddar cheese, divided; 8 large eggs; 2 1/2 cups whole milk; 1 teaspoon Dijon mustard; 1 teaspoon fine sea salt; 1/2 teaspoon freshly ground black pepper; 1/4 teaspoon garlic powder; 1/4 cup sliced green onions, for garnish

By Marcus Bell · Updated April 17, 2026

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This is the dish that makes you look like a hosting genius without any morning panic. An overnight breakfast casserole is assembled the night before, tucked into the fridge while you sleep, and slid into the oven the moment you wake up. By the time everyone is gathered with coffee, you are pulling a golden, puffed, cheese crowned casserole out of the oven.

At its heart this is a savory bread pudding, sometimes called a strata. Cubes of sturdy bread soak overnight in a seasoned egg and milk custard, surrounded by browned sausage, sweet peppers, and plenty of sharp cheddar. The long soak is what transforms ordinary bread into a tender, custardy interior with crisp golden edges.

It is endlessly adaptable and forgiving, which is exactly what you want when feeding a crowd. You can swap the sausage for bacon or keep it vegetarian, use whatever cheese is in the drawer, and stretch it to feed eight hungry people with ease. Leftovers reheat beautifully, so nothing goes to waste.

Below I walk through browning the sausage and aromatics, layering for even distribution, building a properly seasoned custard, and timing the bake so the center sets without drying out. Make it the night before any holiday and your morning becomes effortless.

Why you will love this

Overnight soak: Resting the assembled casserole lets the bread fully absorb the custard for a tender, even, never soggy interior.
Day old bread: Slightly stale bread drinks up the egg mixture and holds its structure instead of collapsing into mush.
Browned sausage and aromatics: Cooking them first builds deep savory flavor and renders off fat that would otherwise pool in the bake.
Generous custard ratio: Eight eggs and rich whole milk give a luxurious, fluffy set that binds everything together.
Make ahead convenience: Assembling the night before turns a fussy brunch dish into a simple bake and serve morning.

What you will need

These are forgiving, swappable ingredients, but a few choices keep the casserole from turning greasy or watery. Read these notes before you shop.

Breakfast sausage (1 pound): Bulk sausage with a little fennel or sage adds the most flavor. Drain it well after browning so the bake is not greasy.
Crusty bread (8 cups): A sturdy loaf like sourdough or a French batard holds up to the soak. Soft sandwich bread turns to paste, so avoid it.
Whole milk (2 1/2 cups): The fat gives a rich, custardy set. You can use half and half for an even more decadent texture.
Eggs (8 large): These are the binder and structure of the whole dish. Whisk them thoroughly so the custard sets evenly throughout.
Sharp cheddar (2 cups): Sharp cheddar melts well and stands up to the sausage. Reserve some for the top to get a browned, bubbly crust.
Dijon mustard (1 teaspoon): A small amount adds a subtle tang that brightens the rich custard without tasting like mustard.
Bell pepper and onion: Diced and sauteed, they add sweetness, color, and moisture balance. Cook them until soft before layering.

Equipment: You need a 9 by 13 inch baking dish, a large skillet, a big mixing bowl, a whisk, and plastic wrap or foil to cover the dish overnight.

How to make it, step by step

Step 1: Brown the sausage and vegetables

Heat a large skillet over medium high and add the sausage, breaking it into crumbles with a wooden spoon. Cook for 5 to 7 minutes until it is browned and no longer pink.

Add the diced onion and bell pepper and cook another 4 to 5 minutes until softened. Drain off the excess fat, then set the mixture aside to cool slightly so it does not cook the eggs later.

Brown the sausage and vegetables

Step 2: Prep the bread and dish

Grease a 9 by 13 inch baking dish well with butter or cooking spray, reaching into the corners. Cut your day old bread into roughly one inch cubes if you have not already.

If your bread is fresh rather than stale, spread the cubes on a sheet pan and toast them at 300 F for about 10 minutes. Drying them out helps them soak up the custard without falling apart.

Step 3: Layer the casserole

Spread half the bread cubes across the bottom of the dish. Scatter half the sausage mixture and a third of the cheese over that first layer.

Repeat with the remaining bread, the rest of the sausage mixture, and another third of the cheese. Reserve the final third of cheese for the top later. Layering rather than dumping ensures every serving has sausage, cheese, and bread.

Step 4: Make the custard

In a large bowl, whisk the eggs until the yolks and whites are fully combined. Add the milk, Dijon, salt, pepper, and garlic powder and whisk again until smooth and uniform.

Taste the raw custard on the tip of a spoon and adjust the salt if it seems flat. Remember the bread and eggs are unseasoned, so the custard needs to be assertively flavored to carry the whole dish.

Step 5: Pour and soak

Slowly pour the custard evenly over the layered bread, making sure to wet every cube. Press the bread down gently with a spatula so it submerges and starts to absorb the liquid.

Cover the dish tightly with plastic wrap and refrigerate for at least 8 hours or overnight. During this rest the bread drinks up the custard and the flavors meld, which is the whole point of an overnight bake.

Do not skip or shorten the soak too much. Under soaked bread bakes up dry and uneven, while a full overnight rest gives that signature tender, sliceable texture.

Pour and soak

Step 6: Bring to room temperature

In the morning, take the casserole out of the fridge and let it sit on the counter for about 30 minutes while the oven heats to 350 F. Starting closer to room temperature helps it bake evenly.

Pulling it straight from the cold fridge into a hot oven can leave the center underdone while the edges overcook. This short rest is a small step that makes a noticeable difference.

Step 7: Bake covered then uncovered

Cover the dish with foil and bake at 350 F for 30 minutes. This first covered stage gently sets the custard without browning the top too soon.

Remove the foil, scatter the reserved cheese over the top, and bake uncovered for another 25 minutes. The casserole should puff up, turn golden, and the cheese should be bubbly and lightly browned.

Check for doneness by inserting a knife into the center, which should come out clean, or by temperature, which should read about 160 F. The center should be set and no longer jiggly when you nudge the pan.

Bake covered then uncovered

Step 8: Rest and serve

Let the casserole rest on the counter for about 10 minutes before cutting. This allows the custard to finish setting so the slices hold together cleanly.

Sprinkle the top with sliced green onions for a fresh, colorful finish. Cut into squares and serve warm, with hot sauce or salsa on the side for anyone who likes a little heat.

Tips for the best results

Use stale bread: Day old or oven dried bread soaks up the custard and holds its shape. Fresh soft bread turns mushy.
Drain the sausage: Pour off rendered fat after browning so the finished casserole is rich but not greasy.
Season the custard well: Salt the egg mixture confidently, since the bread and eggs have none of their own.
Let it come to room temp: Thirty minutes on the counter before baking prevents a cold, underdone center.
Rest before slicing: A 10 minute rest lets the custard set so your squares hold together instead of sliding apart.

Variations and substitutions

Bacon and Gruyere: Swap the sausage for crisp chopped bacon and use nutty Gruyere for a more elegant brunch version.
Vegetarian: Skip the sausage and load up on sauteed mushrooms, spinach, and roasted tomatoes for a meatless bake.
Tex Mex: Use chorizo, pepper jack, and diced green chiles, then serve with avocado and salsa.
Ham and Swiss: Fold in diced cooked ham and shredded Swiss for a flavor that leans toward a classic croque.

How to store and reheat

Cover and refrigerate leftover baked casserole for up to four days. Reheat individual squares in the microwave or warm the whole dish, covered, in a 325 F oven until heated through.

To freeze, cool completely, then wrap portions tightly and freeze for up to two months. Thaw overnight in the fridge and reheat gently so the eggs do not turn rubbery.

What to serve it with

With fresh fruit salad on the side
Alongside a simple green salad for brunch
Topped with hot sauce or a spoon of salsa
With warm biscuits and extra coffee

Frequently asked questions

Can I assemble it the same morning instead of overnight?

You can, but let it sit at least an hour so the bread soaks up the custard. The overnight rest gives the best texture, and a too short soak bakes up dry and uneven.

What bread works best?

Sturdy, slightly stale crusty bread like sourdough, French bread, or a country loaf. Avoid soft sandwich bread, which breaks down into a pasty texture after the long soak.

How do I know when it is done?

The center should be set and no longer jiggly, a knife inserted in the middle should come out clean, and the internal temperature should reach about 160 F.

Can I make it ahead and freeze it?

Yes. You can freeze it either assembled and unbaked or fully baked. Thaw overnight in the refrigerator before baking or reheating for the best texture.

My casserole turned out greasy. What happened?

The sausage was probably not drained. Always pour off the rendered fat after browning the meat so the rich custard is not overwhelmed by grease.

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