There is something magical about pulling a bubbling, golden casserole out of the oven while everyone is still in pajamas. The edges get crisp and toasty, the center stays soft and custardy, and the whole kitchen fills with the cozy aroma of browned sausage, sweet peppers, and melted cheddar. Every forkful is savory, cheesy, and just a little bit indulgent, which is exactly how Christmas morning should taste.
This recipe was made for busy holidays. You do all the work the night before, while the cookies are cooling and the stockings are getting stuffed, then tuck the dish into the fridge. In the morning you let it sit on the counter while the oven heats, slide it in, and enjoy your coffee and gifts while it bakes. It also works beautifully for New Year's Day, a holiday brunch with friends, or any weekend when you have a full house.
SaveI started making this casserole the year I realized I was spending half of Christmas morning at the stove instead of with my family. Now it is our tradition, and the kids ask for it every December. The red and green peppers make it look festive without any extra effort, and I love that one pan feeds a whole crowd with almost no cleanup.
Overnight Christmas Breakfast Casserole
Ingredients
Casserole
Egg Custard
Garnish
Instructions
- Prepare the Baking Dish
Generously butter a 9x13-inch baking dish, covering the bottom and all four sides so the edges release easily after baking. Set it aside while you cook the filling.
- Brown the Sausage
Set a large skillet over medium-high heat and add the sausage. Cook for 7 to 8 minutes, breaking it into small crumbles with a wooden spoon, until it is deeply browned and no pink remains. Transfer the sausage to a paper towel-lined plate and pour off all but a thin film of fat from the skillet.
- Saute the Vegetables
Reduce the heat to medium and melt the 1 tablespoon of butter in the same skillet. Add the onion, red bell pepper, and green bell pepper and cook for 5 to 6 minutes, stirring often, until the onion is translucent and the peppers are tender. Remove the skillet from the heat and let the vegetables cool for a few minutes.
- Start the First Layer
Spread half of the bread cubes in an even layer in the prepared dish. Scatter half of the sausage and half of the pepper and onion mixture over the bread, then sprinkle with 3/4 cup of the cheddar and 1/2 cup of the Monterey Jack.
- Build the Second Layer
Top with the remaining bread cubes, followed by the rest of the sausage and vegetables. Sprinkle the remaining 1/2 cup of Monterey Jack and another 3/4 cup of cheddar over the top. Place the last 1/2 cup of cheddar in a small covered container in the fridge to use when baking.
- Whisk the Egg Custard
In a large bowl, whisk the eggs until the yolks and whites are fully combined. Add the milk, heavy cream, Dijon mustard, salt, black pepper, smoked paprika, and dried thyme, and whisk until smooth with no streaks of egg remaining.
- Pour and Press
Slowly pour the custard evenly over the casserole, making sure to reach the corners. Use a spatula or the back of a large spoon to gently press the bread down so every cube is moistened and soaks up the liquid.
- Chill Overnight
Cover the dish tightly with aluminum foil and refrigerate for at least 8 hours or up to 24 hours. This resting time lets the bread absorb the custard completely, which gives you a tender, evenly set casserole instead of dry pockets.
- Rest and Preheat
In the morning, take the casserole out of the fridge and let it sit on the counter, still covered, for 30 minutes to take the chill off. Meanwhile, preheat your oven to 350°F with a rack in the center position.
- Bake Covered, Then Uncovered
Bake the casserole covered with the foil for 30 minutes. Remove the foil, sprinkle the reserved 1/2 cup of cheddar over the top, and bake uncovered for another 25 minutes, until the top is puffed and golden and a knife inserted in the center comes out clean. The center should read 160°F on an instant-read thermometer.
- Rest and Garnish
Let the casserole rest on a wire rack for 10 minutes so the custard finishes setting and slices cleanly. Sprinkle with the chopped parsley, cut into 12 squares, and serve warm.
Substitutions and variations
- Swap the pork sausage for turkey sausage, diced ham, or crumbled cooked bacon if you prefer a different savory flavor.
- For a vegetarian version, skip the sausage and add 2 cups of sauteed mushrooms and a handful of chopped fresh spinach.
- Use brioche or challah instead of French bread for a softer, slightly sweeter casserole.
- Replace the heavy cream with more whole milk for a lighter custard, or use 2 percent milk throughout if that is what you have on hand.
- Pepper Jack cheese works in place of Monterey Jack if your family likes a little heat.
Chloe's tips
- Day-old bread is key because it soaks up the custard without turning mushy; if your bread is fresh, toast the cubes at 300°F for 10 to 15 minutes to dry them out.
- Let the sausage and vegetables cool slightly before layering so they do not start cooking the eggs or wilt the bread.
- If the top browns too quickly during the uncovered bake, lay a loose sheet of foil over it for the last few minutes.
- A glass or ceramic dish can crack if moved straight from a cold fridge into a hot oven, so do not skip the 30-minute counter rest.
How to store it
- Refrigerate leftovers in an airtight container or covered with foil for up to 4 days.
- Reheat individual squares in the microwave for 60 to 90 seconds, or warm the whole dish covered in a 325°F oven for 20 to 25 minutes.
- To freeze, wrap cooled baked squares individually in plastic wrap and foil and freeze for up to 2 months; thaw overnight in the fridge before reheating.
Serving suggestions
This hearty casserole is a meal on its own, but a few simple sides turn it into a festive holiday brunch spread.
- A bowl of fresh fruit salad with pomegranate seeds and clementine segments
- Warm cinnamon rolls or blueberry muffins for something sweet
- Crispy hash browns or roasted breakfast potatoes
- Hot coffee, orange juice, or sparkling cranberry mimosas
Frequently asked questions
Can I bake this casserole the same day without chilling it overnight?
Yes, but let it rest in the fridge for at least 2 hours so the bread has time to absorb the custard. A shorter soak will give you a slightly drier, less custardy texture, but it will still be delicious.
How do I know when the breakfast casserole is done?
The top should be puffed and golden, the center should not jiggle when you gently shake the dish, and a knife inserted in the middle should come out clean. For certainty, check that the center reaches 160°F on an instant-read thermometer.
Can I make this casserole in a smaller dish?
Absolutely. Halve all of the ingredients and use an 8x8-inch baking dish. Bake covered for 25 minutes, then uncovered for 15 to 20 minutes, checking for doneness the same way.
Why is my breakfast casserole soggy in the middle?
Soggy centers usually come from using fresh bread or underbaking. Use day-old or lightly toasted bread, and give the casserole the full baking time plus the 10-minute rest so the custard can set completely.
Let's get cooking!
Christmas morning is all about slowing down and soaking up the moments with the people you love, and this overnight breakfast casserole gives you the time to do just that. With all the prep done the night before, you get a warm, cheesy, festive breakfast with almost no effort when it matters most. Give it a try this holiday season, and I have a feeling it will become a cherished tradition at your table too. Merry Christmas and happy baking!
