Overnight Christmas Morning Breakfast Casserole

Wake Up to Christmas Breakfast Already Done

Christmas morning should be about pajamas, presents, and coffee — not standing over a stove. That is exactly why this overnight Christmas morning breakfast casserole exists. You assemble everything on Christmas Eve in about 20 minutes: savory breakfast sausage, colorful bell peppers, cubes of hearty bread, and plenty of cheddar, all soaked overnight in a rich egg custard. While the kids tear into gifts, it bakes into a puffy, golden, cheesy masterpiece.

I started making this years ago when I realized I was missing the best part of Christmas morning — watching my family open presents — because I was flipping pancakes. The overnight soak is the real secret: the bread absorbs the seasoned custard like a savory bread pudding, so every bite is custardy in the center with crisp, cheesy edges. It feeds ten hungry people from one dish, and there is genuinely nothing to do in the morning except preheat the oven.

Why You’ll Love This Recipe

• Zero morning work. Assemble on Christmas Eve, refrigerate overnight, and just bake in the morning.
• Feeds a crowd. One 9×13 dish generously serves 10 — perfect for family staying over.
• Custardy, cheesy, golden. The overnight soak creates a texture somewhere between strata and savory bread pudding.
• Customizable. Swap the sausage for bacon or ham, add any vegetables you like, change the cheese.
• Holds beautifully. It stays warm and delicious on the table through a long, leisurely gift-opening session.

Ingredients

• 1 pound bulk breakfast sausage (mild or hot)
• 1 medium yellow onion, diced
• 1 red bell pepper, diced
• 1 green bell pepper, diced
• 8 large eggs
• 2 cups whole milk
• 1 teaspoon dry mustard powder
• 1/2 teaspoon kosher salt
• 1/4 teaspoon black pepper
• 1/4 teaspoon smoked paprika (optional)
• 6 cups cubed day-old bread (about 3/4 of a loaf — French, sourdough, or Italian)
• 2 cups shredded sharp cheddar cheese, divided
• 2 green onions, sliced, for garnish (optional)

A few notes on key ingredients: Day-old bread is important — fresh bread turns to mush, while slightly stale bread soaks up the custard without disintegrating. If your bread is fresh, cube it and dry the cubes in a 300°F oven for 10 minutes. Whole milk makes the richest custard; 2% works but the texture is a little less luxurious. Dry mustard powder is the quiet hero here — you will not taste “mustard,” but it sharpens the cheese flavor noticeably. Shred your own cheddar if you can; pre-shredded cheese contains anti-caking starch that prevents smooth melting.

How to Make Overnight Christmas Morning Breakfast Casserole

1. Brown the sausage. In a large skillet over medium-high heat, cook the breakfast sausage, breaking it into crumbles with a wooden spoon, for 8 to 10 minutes until browned and cooked through. Transfer to a paper-towel-lined plate to drain. Do not wipe out the skillet — that flavorful fat is gold.
2. Soften the vegetables. In the same skillet over medium heat, sauté the diced onion and bell peppers in the reserved sausage drippings (add a teaspoon of oil if the pan is dry) for 5 to 6 minutes, until softened and the onion is translucent. Let cool slightly.
3. Whisk the custard. In a large bowl, whisk together the eggs, milk, dry mustard, salt, pepper, and smoked paprika if using, until completely smooth and slightly frothy. This seasoned custard is what transforms plain bread into something special.
4. Combine everything. Add the bread cubes, cooked sausage, sautéed vegetables, and 1 1/2 cups of the cheddar to the custard. Stir gently but thoroughly so every bread cube gets coated. Let the mixture sit for 5 minutes so the bread begins absorbing the custard.
5. Transfer to the baking dish. Grease a 9×13-inch baking dish and spread the mixture evenly into it, pressing down lightly so the top is fairly level. An even layer bakes evenly — mounded centers stay soupy while thin edges overcook.
6. Refrigerate overnight. Cover tightly with plastic wrap or foil and refrigerate for at least 8 hours, or up to 24 hours. During this long soak, the bread fully absorbs the custard, which is what creates the creamy, cohesive texture.
7. Christmas morning: preheat. When you wake up, remove the casserole from the refrigerator and let it sit on the counter for 20 to 30 minutes while the oven preheats to 350°F. Taking the chill off helps it bake evenly.
8. Top with cheese and bake. Uncover the casserole and sprinkle the remaining 1/2 cup of cheddar over the top. Bake at 350°F for 45 to 55 minutes, until puffed, deep golden brown on top, and set in the center — a knife inserted in the middle should come out clean with no wet egg.
9. Rest before slicing. Let the casserole rest for 10 minutes. Like a frittata, it needs this time for the custard to fully set; cutting too early gives you a soupy slice.
10. Serve warm. Cut into squares and serve with sliced green onions scattered over the top. Offer hot sauce, salsa, or maple syrup at the table and let everyone customize. Pair with fresh fruit and coffee for the complete Christmas morning spread.

Pro Tips for the Best Results

• Do not skip the overnight rest. A minimum 8-hour soak is what separates a great strata from a pile of eggy bread. The bread needs time to fully absorb the custard.
• Drain the sausage well. Excess grease pools at the bottom of the dish and makes the casserole oily. A paper-towel-lined plate does the job.
• Use a deep baking dish. The casserole puffs significantly as it bakes. A standard 9x13x2-inch dish contains it; anything shallower will overflow.
• Tent with foil if browning too fast. If the top is deeply golden but the center is not set, cover loosely with foil for the remaining bake time.
• Check doneness with a knife, not a jiggle. The center should not wobble when you gently shake the dish. A clean knife test is the most reliable sign it is done.
• Keep it warm for late risers. Cover the baked casserole loosely with foil and hold it in a 200°F oven for up to 45 minutes — perfect for families that open gifts at different speeds.

Variations

• Bacon and Swiss. Swap the sausage for 12 ounces of cooked, crumbled bacon and the cheddar for shredded Swiss or Gruyère. Add 1 cup of sautéed mushrooms for an earthy, upscale twist.
• Ham and Veggie. Use 2 cups of diced leftover holiday ham instead of sausage, and load up the vegetables — spinach, mushrooms, and sun-dried tomatoes are all excellent here.
• Southwestern. Use chorizo instead of breakfast sausage, pepper jack instead of cheddar, and add a 4-ounce can of diced green chiles. Serve with salsa, sour cream, and avocado.
• Vegetarian. Skip the meat entirely and double the vegetables — add mushrooms, zucchini, and spinach. Use vegetable broth in place of 1/2 cup of the milk for extra savory depth.

Storage & Reheating

Refrigerate leftovers in an airtight container for up to 4 days. Reheat individual squares in the microwave for 60 to 90 seconds, or warm the whole dish covered with foil in a 350°F oven for 20 minutes until the center reaches 165°F, following USDA food safety guidance for egg dishes. This casserole also freezes well: cool completely, wrap portions tightly, and freeze up to 2 months. Thaw overnight in the refrigerator before reheating. The unbaked assembled casserole can be refrigerated up to 24 hours before baking — do not push it longer or the texture suffers.

Frequently Asked Questions

Can I assemble this overnight Christmas morning breakfast casserole two nights ahead?

Stick to one night. Up to 24 hours of soaking gives you the perfect custardy texture, but beyond that the bread breaks down too much and the casserole turns dense and soggy. Assemble on Christmas Eve for Christmas morning — that timing is ideal.

Why is the center of my casserole still wet?

It likely needs more time. Ovens vary, and a very full dish can take up to 60 minutes. Make sure the dish is not overfilled, let the casserole sit at room temperature 20 to 30 minutes before baking, and verify doneness with a knife in the absolute center — it should come out clean.

Can I use croissants or brioche instead of regular bread?

Yes, and it is delicious — richer, almost dessert-like. Use slightly less milk (1 3/4 cups) since enriched breads absorb less liquid, and expect a softer, more indulgent texture. Stale croissants from the bakery bargain bin are perfect for this.

How do I keep the casserole warm while we open gifts?

Bake it, then tent loosely with foil and hold in a 200°F oven for up to 45 minutes. The texture stays excellent. Alternatively, assemble it so it finishes baking right as gift-opening winds down — the 10-minute rest gives you a natural buffer.

Can I make a smaller batch for just a few people?

Absolutely. Halve all ingredients and bake in an 8×8-inch dish for 35 to 45 minutes at 350°F. The method is identical — just check for doneness a little earlier since the smaller dish bakes faster.

This overnight Christmas morning breakfast casserole lets you actually enjoy Christmas morning instead of cooking through it — and that might be the best gift of all. Assemble it on Christmas Eve, sleep well, and wake up to a house that smells amazing. Round out your holiday menu with our cranberry jalapeño cream cheese dip for grazing, and save room the next day for leftover Thanksgiving turkey casserole style comfort. For more make-ahead ideas, see our easy meal prep recipes.