Christmas Morning Breakfast Casserole (Make-Ahead Holiday Breakfast)

Christmas morning should smell like cinnamon candles, sound like tearing wrapping paper, and taste like something spectacular that you did NOT wake up at 5 a.m. to cook. Enter this Christmas morning breakfast casserole: a fluffy, cheesy, sausage-loaded egg bake that you assemble the night before, tuck into the fridge, and slide into the oven while the coffee brews. By the time the presents are open, your kitchen smells like a holiday miracle and you look like a genius.

This is a classic strata-style breakfast casserole at heart. Chunks of brioche soak up a rich egg-and-milk custard overnight, turning into a puffy, savory bread pudding studded with browned breakfast sausage, sharp cheddar, sweet red bell pepper, and green onions. It feeds a crowd from one pan, reheats beautifully, and has exactly the kind of golden, bubbly top that makes everyone reach for seconds.

One pan, twenty minutes of real effort, zero Christmas-morning panic. Let’s get it in the fridge tonight.

Recipe at a Glance

• Prep time: 20 minutes
• Chill time: Overnight (8 to 12 hours)
• Bake time: 45 to 60 minutes
• Total time: 9 to 13 hours (mostly hands-off)
• Yield: 9×13-inch pan
• Servings: 8 to 10
• Oven: 350°F (175°C)
• Category: Christmas breakfast and holiday brunch

Why This Method Works

The magic of this Christmas morning breakfast casserole is not a fancy ingredient. It is time. When cubed bread sits in an egg-and-milk custard overnight in the refrigerator, the starch granules slowly hydrate and swell, drawing the seasoned custard deep into every crumb. This is the same principle behind Nagi’s much-loved cheese-and-bacon breakfast strata: a long, cold soak turns individual bread cubes into one cohesive, puffy, custardy whole instead of a dish of croutons floating in scrambled egg.

Day-old brioche or sandwich bread works best because slightly dried bread is thirstier. It drinks up more custard and then bakes into tender pockets rather than mush. Browning the sausage before assembly matters too: it renders out the fat (so the custard never turns greasy) and adds those crispy, caramelized bits that give every bite depth. The gentle 350°F bake then sets the eggs gradually from edge to center, so the top turns deeply golden while the middle stays silky, not rubbery.

Food safety rides along with the method. The assembled casserole must go straight into the refrigerator, not sit on the counter, and bake until the center is fully set. According to safe egg handling guidance, egg dishes like this should reach 160°F internally. Trust the thermometer on your first bake and the visual cues every time after that.

Ingredients

• 1 pound breakfast sausage (pork or turkey)
• 8 cups cubed day-old brioche or sturdy white sandwich bread, cut into 1-inch cubes (about 1 pound loaf)
• 2 cups shredded sharp cheddar cheese, divided
• 1 medium red bell pepper, diced
• 4 green onions, thinly sliced, plus extra for garnish
• 12 large eggs
• 2 1/2 cups whole milk
• 1 teaspoon Dijon mustard
• 1 teaspoon kosher salt
• 1/2 teaspoon black pepper
• 1/2 teaspoon garlic powder (optional)
• Butter or cooking spray, for the baking dish

Directions

1. Butter a 9×13-inch baking dish generously (or coat with cooking spray). Set it near your stove so assembly is easy.
2. Brown the sausage: cook it in a large skillet over medium-high heat, breaking it into crumbles, for 7 to 8 minutes until no pink remains and the edges are browned. Drain off the excess fat on a paper-towel-lined plate.
3. Spread half the bread cubes in the bottom of the prepared dish. Top with half the cooked sausage, 1 cup of the cheddar, the diced red bell pepper, and the sliced green onions. Add the remaining bread cubes, sausage, and another 1/2 cup of cheddar. Finish with the final 1/2 cup of cheese on top.
4. Whisk the eggs: in a large bowl, whisk the 12 eggs with the milk, Dijon mustard, salt, black pepper, and garlic powder until completely smooth and slightly frothy, about 1 minute.
5. Pour the custard evenly over everything in the dish. Press the bread down gently with a spatula so every cube gets soaked. If a few dry corners pop up, spoon a little custard over them.
6. Cover the dish tightly with plastic wrap or foil and refrigerate for at least 8 hours, and up to 24 hours. (Short on time? A 1-hour minimum soak works, but overnight gives the custardy texture this dish is famous for.)
7. In the morning, take the casserole out of the fridge while the oven preheats to 350°F (175°C). Let it sit at room temperature for 15 to 20 minutes to take the chill off.
8. Bake uncovered for 45 to 60 minutes, until the top is deeply golden and puffed, the edges are pulling away from the dish, and the center has no jiggle when you gently shake the pan. A knife inserted near the center should come out clean, and an instant-read thermometer should read 160°F in the middle. If the top browns too fast, tent it loosely with foil for the last 15 minutes.
9. Rest for 10 minutes before slicing. This settles the custard so the slices cut cleanly. Scatter extra sliced green onions over the top and serve warm.

Pro Tips

• Use day-old bread on purpose. Fresh, soft bread soaks up custard too fast and turns to mush. If your loaf is fresh, cut it into cubes and leave them uncovered on a baking sheet for a few hours, or toast them at 300°F for 10 minutes.
• Grate your own cheddar. Pre-shredded cheese is coated with anti-caking starch that dulls the melt. A block of sharp cheddar and five minutes with a box grater gives you dramatically gooier, richer pockets of cheese.
• Drain that sausage well. Excess pork fat pooling in the dish is the number-one cause of a greasy bottom layer. Press the crumbles on paper towels after browning.
• Season the custard, not just the layers. The Dijon, salt, and garlic powder go in the egg mixture so every bite is seasoned evenly. Bland custard equals bland casserole.
• Let it rest. Ten minutes of resting feels like an eternity on Christmas morning, but slicing early lets the custard run. The rest is what gives you clean, sliceable squares.

Common Mistakes to Avoid

• Under-soaking the bread. Pouring the custard and baking right away gives you a dish of dry-topped croutons in scrambled egg. The overnight soak is the whole point. If you must bake sooner, give it at least 1 hour of soak time.
• Pulling it too early. A jiggly center means raw custard, not creamy texture. Bake until there is no wobble in the middle and the center reads 160°F on a thermometer. Golden does not always mean done.
• Skipping the sausage browning. Raw sausage crumbles mixed straight into the casserole steam instead of brown, and they release fat and water into the custard. Always brown and drain first.
• Overcrowding with add-ins. This casserole is forgiving, but every extra cup of vegetables or meat needs its share of custard. Stick close to the ratios here, or add 2 extra eggs if you bulk it up.
• Forgetting the foil tent. Cheese-heavy casseroles brown fast. If the top is golden at 30 minutes but the center still jiggles, tent with foil and keep baking. Color is not a doneness timer.

Easy Substitutions

• Sausage: Swap in crumbled cooked bacon, diced ham, or chorizo for a smoky twist. For a vegetarian version, use sauteed mushrooms and an extra bell pepper instead.
• Cheese: Monterey Jack, Gruyere, or a Swiss-cheddar blend all melt beautifully here. Pepper Jack adds a little holiday heat.
• Bread: Any sturdy bread works: sourdough, challah, French bread, or even leftover dinner rolls. Skip very soft sandwich bread if it is fresh, or dry the cubes first.
• Milk: Half-and-half or a splash of heavy cream in place of some of the milk makes a richer, more decadent custard. Whole milk is the sweet spot for everyday.
• Peppers and onions: Swap the red bell pepper for roasted poblanos, sun-dried tomatoes, or sauteed spinach (squeeze it very dry first). If you want a sweet option for the other side of the table, pair this with our easy cinnamon French toast sticks, which kids go wild for.

Storage and Make-Ahead

The make-ahead part is the whole point: assemble the casserole the night before (up to 24 hours ahead), cover tightly, and refrigerate. Move it from the fridge to the oven on Christmas morning, adding 5 to 10 extra minutes of bake time since it goes in cold.

Baked leftovers keep in an airtight container in the refrigerator for up to 4 days. Reheat individual slices in the microwave for 1 to 2 minutes, or warm the whole pan covered with foil at 325°F for about 20 minutes until hot through. The baked casserole also freezes well: cool it completely, wrap slices tightly in plastic wrap and foil, and freeze for up to 2 months. Thaw overnight in the fridge before reheating. Remember the two-hour rule: the assembled casserole should go into the refrigerator within 2 hours of mixing, and leftovers should be chilled within 2 hours of serving.

Hosting a full Christmas morning spread? This casserole sits happily next to a tray of our bakery-style pumpkin muffins and a big skillet of our easy one-pan breakfast hash for a table that looks like you hired a caterer.

Frequently Asked Questions

Can I make Christmas breakfast casserole the night before?

Yes, that is exactly how it is designed to be made. Assemble the full casserole in the baking dish, cover it tightly, and refrigerate for 8 to 24 hours. In the morning, let it sit out for 15 to 20 minutes while the oven preheats, then bake as directed, adding 5 to 10 minutes if it goes in cold. Do not leave the assembled casserole at room temperature for more than 2 hours.

What temperature is a breakfast casserole done?

An egg breakfast casserole is done when the center reaches 160°F on an instant-read thermometer and a knife inserted near the center comes out clean. Visually, the top should be deeply golden and puffed, the edges pulling away from the dish, and the center should have no jiggle when you gently shake the pan.

Why is my breakfast casserole soggy?

Sogginess usually comes from too much custard for the bread, an under-soak, or underbaking. Keep to the 12 eggs and 2 1/2 cups of milk for 8 cups of bread cubes, give the full overnight soak, and bake until the center is fully set with no wobble. Resting 10 minutes before slicing also lets the custard firm up so slices hold together.

Can I make this breakfast casserole without the overnight chill?

You can, but give it at least a 1-hour soak in the refrigerator before baking so the bread absorbs the custard. Bake it covered with foil for the first 25 minutes, then uncovered, until the center is set. The texture will be good, but the overnight version is noticeably puffier and more custardy because the slow cold soak hydrates the bread fully.