Breakfast Will Be Served: Overnight Egg Casserole

This overnight egg casserole is the answer to serving a hot, hearty breakfast to a crowd without standing over the stove. Layers of bread, sausage, cheese, and a seasoned egg custard soak overnight, then bake into a golden, puffed casserole that slices cleanly. It is a classic American brunch dish, often called a strata or overnight breakfast bake, and it works because the overnight rest lets the bread absorb the custard, creating a tender, soufflé-like texture with a savory, satisfying crust.

Ingredients

1 lb (450 g) bulk breakfast sausage (or mild Italian sausage, casings removed)
1 tbsp (15 ml) olive oil
1 medium yellow onion, diced (about 1 cup / 150 g)
1 red bell pepper, diced (about 1 cup / 150 g)
8 large eggs
2 cups (480 ml) whole milk
1 tsp (5 g) Dijon mustard
1/2 tsp (1 g) smoked paprika
1/2 tsp (1.5 g) garlic powder
1/2 tsp (2.5 g) salt, plus more to taste
1/4 tsp (0.5 g) black pepper
6 cups (170 g) cubed day-old bread (French or sourdough, crusts on)
2 cups (226 g) shredded sharp cheddar cheese, divided
2 tbsp (30 g) unsalted butter, melted (for greasing the dish)

Instructions

Heat a large skillet over medium heat. Add the sausage and cook, breaking it into small pieces with a spoon, until browned and cooked through, about 8–10 minutes. Transfer to a plate lined with paper towels to drain. (The sausage is fully cooked when it reaches 160°F (71°C) as measured with a food thermometer.)
Wipe the skillet clean, add the olive oil, and heat over medium. Add the onion and bell pepper, and cook until softened, about 5–7 minutes. Remove from heat.
In a large bowl, whisk together the eggs, milk, Dijon mustard, smoked paprika, garlic powder, salt, and black pepper until fully combined.
Grease a 9×13-inch (23×33 cm) baking dish with the melted butter. Spread the bread cubes evenly in the dish. Scatter the cooked sausage, onion, and bell pepper over the bread. Sprinkle with 1 1/2 cups (170 g) of the shredded cheddar cheese.
Pour the egg mixture evenly over the top, making sure all the bread is moistened. Sprinkle the remaining 1/2 cup (56 g) of cheese on top. Cover the dish with plastic wrap or foil and refrigerate for at least 6 hours, or overnight (up to 24 hours).
When ready to bake, preheat the oven to 350°F (175°C). Remove the casserole from the refrigerator and let it sit at room temperature for 20–30 minutes while the oven heats.
Bake uncovered for 50–60 minutes, until the casserole is puffed, golden brown, and the center is set (a knife inserted into the middle comes out clean, and the internal temperature reaches 160°F (71°C) for egg dishes). If the top is browning too quickly, loosely cover with foil after 30 minutes.
Let rest for 10 minutes before slicing and serving.

Tips

Bread choice: Use day-old or slightly stale bread; it absorbs the custard better without turning mushy. If your bread is fresh, toast the cubes in a 300°F (150°C) oven for 5–10 minutes to dry them out.
Don’t skip the overnight rest: The minimum is 6 hours, but 8–12 is ideal. This allows the bread to soak up the custard, giving the casserole its signature creamy interior.
Make it ahead: You can assemble the casserole up to 24 hours in advance. If you need to bake it sooner than 6 hours, reduce the bread to 5 cups (140 g) to prevent a soggy center.
Check for doneness: The center should read 160°F (71°C) on an instant-read thermometer. If the top is getting too dark before the center is set, cover with foil and continue baking.

Serving Suggestions

Serve this casserole warm, cut into squares, with a side of fresh fruit or a simple green salad. It pairs beautifully with roasted potatoes, a dollop of sour cream, or a drizzle of hot sauce. For a complete brunch spread, add a basket of toasted bagels or croissants and a carafe of fresh orange juice.

Variations

Vegetarian: Omit the sausage and add 1 cup (150 g) of sautéed mushrooms and 1 cup (150 g) of chopped spinach (squeezed dry) with the onions and peppers.
Ham and Swiss: Replace the sausage with 1 1/2 cups (200 g) of diced cooked ham and use Swiss cheese instead of cheddar.
Southwest: Add 1 can (4 oz / 113 g) of diced green chiles, 1/2 tsp (1 g) of cumin, and use Monterey Jack cheese. Serve with salsa and avocado.
Herb and goat cheese: Add 2 tbsp (8 g) of chopped fresh chives and 1 tbsp (3 g) of chopped fresh thyme to the egg mixture, and crumble 4 oz (113 g) of goat cheese over the top before baking.

Storage and Reheating

Refrigerate leftovers in an airtight container within 2 hours of baking. They will keep for up to 4 days. To reheat, place a serving on a microwave-safe plate and heat in 30-second bursts until warmed through, or reheat in a 350°F (175°C) oven for 10–15 minutes. The casserole can also be frozen after baking: wrap individual portions in plastic wrap and then foil, and freeze for up to 2 months. Thaw overnight in the refrigerator before reheating.

Frequently Asked Questions

Can I use a different type of bread? Yes, any sturdy bread works—French, sourdough, ciabatta, or even whole wheat. Avoid very soft sandwich bread, which can become too mushy.

Can I make this without meat? Absolutely. Simply omit the sausage and add an extra cup of vegetables, such as mushrooms, zucchini, or broccoli. You may want to add a pinch of red pepper flakes for a little heat.

Why is my casserole watery? This can happen if the bread was too fresh or if you used low-fat milk. Use day-old bread and whole milk for the best texture. Also, make sure to drain any excess fat from the sausage and squeeze dry any vegetables that release water (like spinach).

Can I bake it immediately without refrigerating? You can, but the texture will be different—the bread won’t absorb as much custard, and the casserole will be more like a frittata. If you do bake immediately, reduce the baking time to 35–40 minutes and check for doneness.

How do I know when it’s done? The top should be golden brown and puffed, and a knife inserted into the center should come out clean. For food safety, the internal temperature should reach 160°F (71°C).

Can I use egg substitute? Yes, you can use 2 cups (480 ml) of liquid egg substitute instead of the 8 eggs. The texture will be slightly less fluffy, but it will still taste great.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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