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Golden baked Christmas breakfast casserole in a white dish with cheese and parsley.

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.
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Prep Time 20 minutes
Cook Time 55 minutes
Total Time 1 hour 15 minutes
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
 

  1. Grease a 9x13-inch baking dish with the butter. Spread the cubed bread evenly in the dish and set aside.
  2. 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.
  3. 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.
  4. In a large bowl, whisk the eggs, milk, half-and-half, Dijon, kosher salt, black pepper, garlic powder, and smoked paprika until well combined.
  5. Add the cooked sausage, sautéed vegetables, scallions, parsley, cheddar, and mozzarella to the bowl. Stir to combine.
  6. Pour the mixture evenly over the bread cubes, pressing lightly so the bread is mostly submerged. Cover tightly with foil or plastic wrap.
  7. Refrigerate at least 6 hours or up to 24 hours to allow the bread to absorb the custard.
  8. 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.
  9. 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.
  10. 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.