On Christmas morning, I want coffee, pajamas, and something hot bubbling in the oven with zero effort. This overnight Christmas breakfast casserole checks every box. I assemble it the night before, tuck it in the fridge, then just bake while the tree lights are twinkling.

It’s hearty with eggs, sausage, cheese, and soft custardy bread under a golden, toasty top. The texture is like a savory bread pudding, and the flavors feel special without being fussy. Add fruit and cocoa and you’re done.

Why this breakfast casserole works

This casserole uses a smart ratio of eggs, milk, and bread so it bakes up creamy in the middle with a golden, lightly crisp top. A quick Dijon and spice mix seasons the custard so every bite tastes balanced, not bland. Cubed day-old bread soaks overnight, which means the morning bake is hands-off and the dish slices cleanly.

It’s flexible too. Use breakfast sausage or bacon, cheddar or whatever cheese you have, and toss in peppers or spinach. The base is forgiving, so it still turns out beautifully even if you tweak a few things to fit what’s in your fridge.

Ingredients you’ll need

Classic breakfast staples come together here. Day-old bread, eggs, breakfast sausage, and a mix of cheeses make the base, while a touch of Dijon and paprika adds warmth and depth.

8 cups day-old French or sourdough bread, cut into 1-inch cubes
1 tbsp unsalted butter, for greasing the dish
1 lb breakfast sausage, casings removed if linked
1 small yellow onion, finely chopped
1 red bell pepper, diced
10 large eggs
2 cups whole milk
1 cups half-and-half
1 tbsp Dijon mustard
1 1/2 tsp kosher salt, plus more to taste
1 tsp black pepper, freshly ground
1 tsp garlic powder
1/2 tsp smoked paprika
2 cups sharp cheddar cheese, shredded
1 cups mozzarella cheese, shredded
2 scallions, thinly sliced, white and green parts
2 tbsp fresh parsley, chopped, plus more for garnish
red pepper flakes, optional, to taste

How to make it

Assemble the casserole the night before, chill, then bake in the morning until puffed and set.

Grease a 9×13-inch baking dish with the butter. Spread the cubed bread evenly in the dish and set aside.
In a large skillet over medium heat, cook the sausage, breaking it up with a spoon, until browned and cooked through, 6 to 8 minutes. Transfer to a paper towel–lined plate, leaving about 1 tablespoon of drippings in the pan.
Add the onion and bell pepper to the skillet with a pinch of salt; sauté until softened and most moisture has cooked off, 5 to 6 minutes. Remove from heat and cool slightly.
In a large bowl, whisk the eggs, milk, half-and-half, Dijon, kosher salt, black pepper, garlic powder, and smoked paprika until well combined.
Add the cooked sausage, sautéed vegetables, scallions, parsley, cheddar, and mozzarella to the bowl. Stir to combine.
Pour the mixture evenly over the bread cubes, pressing lightly so the bread is mostly submerged. Cover tightly with foil or plastic wrap.
Refrigerate at least 6 hours or up to 24 hours to allow the bread to absorb the custard.
When ready to bake, preheat the oven to 350°F (175°C). Uncover the casserole and let it sit at room temperature while the oven heats, about 15 minutes.
Bake uncovered until puffed, the edges are golden, and the center is just set, 45 to 55 minutes. If the top browns too quickly, tent loosely with foil during the last 10 to 15 minutes.
Rest 10 minutes before slicing. Garnish with extra parsley and a pinch of red pepper flakes if using, then serve warm.

Storage, make-ahead and reheating

Assemble the casserole up to 24 hours in advance, cover tightly, and refrigerate. In the morning, remove it from the fridge while the oven preheats so the dish isn’t going from very cold to very hot. Bake until the center is just set and the top is lightly browned.

Leftovers keep well. Cool completely, then cover and refrigerate for up to 4 days. Reheat slices in a 325°F (165°C) oven for 10 to 15 minutes, or microwave gently in 30-second bursts until warmed through. You can also freeze tightly wrapped portions for up to 2 months; thaw overnight in the fridge and reheat as above.

Common mistakes to avoid

Using fresh, super-soft bread: Fresh bread doesn’t absorb the custard well and can turn mushy. Use day-old or lightly toasted bread cubes.
Skipping the chill time: The overnight soak lets the eggs absorb evenly, so you get a custardy center rather than dry edges and a wet middle.
Overloading with veggies without pre-cooking: Raw vegetables release water and make the casserole soggy. Sauté them until tender and let cool before adding.
Undersalting the custard: The custard seasons the entire dish. Taste a tiny spoon of the mixture (before adding raw meat drippings) to make sure it’s pleasantly seasoned.
Overbaking: If you bake until the top is very brown and the center is firm, it can dry out. Pull it when the center barely jiggles and a knife comes out with moist crumbs, not wet egg.

Overhead of baked breakfast casserole cut into squares.

Variations and substitutions

Meat swaps: Use cooked crumbled bacon, diced ham, or chicken-apple sausage in place of breakfast sausage. Keep total cooked meat around 1 to 1 1/4 pounds.
Cheese options: Try Gruyère, Monterey Jack, pepper jack, Swiss, or a mix. Keep about 2 1/2 to 3 cups total shredded cheese.
Veggie boost: Add 2 cups sautéed mushrooms, spinach (squeezed dry), or roasted broccoli. Cook off moisture first.
Gluten-free: Use your favorite sturdy gluten-free boule or sandwich bread, toasted before cubing.
Dairy tweaks: Replace half-and-half with whole milk for a lighter texture, or use all half-and-half for a richer bite.
Spice it up: Add red pepper flakes, a pinch of cayenne, or hot sauce to the custard for gentle heat.

What to serve with it

Keep the rest of breakfast simple. A bright quick bread like this cranberry orange loaf with fresh citrus glaze is a cheerful contrast. For a warm drink, set out a slow cooker of creamy crockpot hot chocolate so guests can help themselves.

If your morning includes snacks and sips, a tray of cranberry brie bites makes a lovely small bite, and a pot of stovetop mulled wine is cozy for later in the day.

Your questions, answered

Can I bake this casserole right away instead of overnight?

Yes. If you’re short on time, let the assembled casserole rest at room temperature for 20 to 30 minutes so the bread starts to absorb the custard, then bake. The texture won’t be quite as custardy as the overnight version, but it will still be delicious.

What kind of bread works best?

Use a sturdy loaf like French, Italian, sourdough, or brioche. Day-old is ideal. If your bread is fresh, cube it and toast on a sheet pan at 300°F (150°C) for 10 to 12 minutes to dry it out before assembling.

How do I know when the casserole is done?

Look for a puffed top and barely set center. Insert a thin knife in the middle; it should come out with moist crumbs but not wet egg. If the top is browning quickly, tent loosely with foil for the last 10 to 15 minutes.

Can I make this without sausage?

Absolutely. Skip the sausage and add 2 more cups of sautéed vegetables, plus an extra 1/2 teaspoon of salt to make up for the seasoning the sausage would have added. You can also use plant-based sausage.

How do I scale this for a crowd?

Double the recipe and bake in two 9×13-inch dishes. Rotate the pans halfway through for even browning. Start checking for doneness around 40 minutes and add time as needed.

A cozy note to end on

I hope this easy make-ahead breakfast frees you up to enjoy a slow Christmas morning. Mix it up, tuck it in the fridge, and let the oven do the work while you sip coffee by the tree.

Christmas Breakfast Casserole (Make-Ahead Overnight)

A cozy overnight breakfast casserole with eggs, sausage, cheese and bread. Assemble ahead and bake on Christmas morning until puffed and golden.

Print Recipe Pin Recipe

Prep Time 20

Cook Time 55

Total Time 1 15

Servings: 10 servings

Course: Breakfast

Cuisine: American

Calories: 460

Ingredients Method Notes

Ingredients

8 cups day-old French or sourdough bread cut into 1-inch cubes
1 tbsp unsalted butter for greasing the dish
1 lb breakfast sausage casings removed if linked
1 small yellow onion finely chopped
1 red bell pepper diced
10 large eggs
2 cups whole milk
1 cups half-and-half
1 tbsp Dijon mustard
1 1/2 tsp kosher salt plus more to taste
1 tsp black pepper freshly ground
1 tsp garlic powder
1/2 tsp smoked paprika
2 cups sharp cheddar cheese shredded
1 cups mozzarella cheese shredded
2 scallions thinly sliced, white and green parts
2 tbsp fresh parsley chopped, plus more for garnish
red pepper flakes optional, to taste

Method

Grease a 9×13-inch baking dish with the butter. Spread the cubed bread evenly in the dish and set aside.
In a large skillet over medium heat, cook the sausage, breaking it up with a spoon, until browned and cooked through, 6 to 8 minutes. Transfer to a paper towel–lined plate, leaving about 1 tablespoon of drippings in the pan.
Add the onion and bell pepper to the skillet with a pinch of salt; sauté until softened and most moisture has cooked off, 5 to 6 minutes. Remove from heat and cool slightly.
In a large bowl, whisk the eggs, milk, half-and-half, Dijon, kosher salt, black pepper, garlic powder, and smoked paprika until well combined.
Add the cooked sausage, sautéed vegetables, scallions, parsley, cheddar, and mozzarella to the bowl. Stir to combine.
Pour the mixture evenly over the bread cubes, pressing lightly so the bread is mostly submerged. Cover tightly with foil or plastic wrap.
Refrigerate at least 6 hours or up to 24 hours to allow the bread to absorb the custard.
When ready to bake, preheat the oven to 350°F (175°C). Uncover the casserole and let it sit at room temperature while the oven heats, about 15 minutes.
Bake uncovered until puffed, the edges are golden, and the center is just set, 45 to 55 minutes. If the top browns too quickly, tent loosely with foil during the last 10 to 15 minutes.
Rest 10 minutes before slicing. Garnish with extra parsley and a pinch of red pepper flakes if using, then serve warm.

Notes

If your bread is very soft, toast the cubes briefly so they hold texture after soaking.

For a richer casserole, swap the milk for more half-and-half; for lighter, use all milk.

You can assemble directly in the baking dish or in a large bowl, then transfer for neater distribution.

Leftover slices reheat best in the oven so the top stays a little crisp.

About the Author

Tamás Puskás Owner of Home Style Vibes

Owner of Home Style Vibes

Tamás Puskás is the owner and editor of Home Style Vibes, a cozy-modern lifestyle blog about creating a home you truly love. Right now he's building a new family home from the ground up, so he deals with the same questions readers ask every day: which materials actually last, what's worth the money, and how to make a house feel like home without the overwhelm. Home Style Vibes covers home decor, DIY projects, cleaning and organization, easy family recipes, plants, and seasonal ideas. Everything is practical, tested, and made for real family life with a little one at home.