Overnight Sausage and Egg Breakfast Casserole

If you're hosting a holiday brunch or just don't want to think about breakfast before coffee, this is the recipe to make the night before. Overnight Sausage and Egg Breakfast Casserole layers bread, sausage, and cheese, then soaks overnight in a seasoned egg custard — so by morning, all that's left to do is bake it.

Why the Overnight Step Actually Matters

This isn't just a make-ahead convenience — the resting time changes the texture. Bread cubes that go straight into the oven with raw egg custard bake up with a noticeably drier, more uneven texture, because the bread hasn't had time to fully absorb the liquid. Given at least 8 hours in the fridge, the bread soaks all the way through and bakes into something closer to a savory bread pudding: custardy in the middle, with a golden, slightly crisp top.

What You'll Need

• 1 pound breakfast sausage, uncooked
• 6 cups day-old bread, cubed (French bread or sourdough works well)
• 2 cups shredded cheddar cheese
• 8 large eggs
• 2 cups whole milk
• 1 teaspoon dry mustard powder
• ½ teaspoon garlic powder
• ½ teaspoon salt
• ¼ teaspoon black pepper
• 2 green onions, sliced (optional, for topping)

A note on the bread: day-old or slightly stale bread is genuinely better here, not just a use-it-up suggestion. Fresh, soft bread tends to turn to mush once it's soaked overnight, while bread that's a day or two old (or lightly toasted) holds its shape and gives the casserole some texture instead of a uniformly soft crumb.

How to Make It

1. Brown the sausage — Cook in a skillet over medium heat, breaking it into crumbles, until no pink remains. Drain the excess grease.
2. Layer the dish — Spread the bread cubes in a greased 9x13-inch baking dish. Scatter the cooked sausage and shredded cheddar on top.
3. Make the custard — Whisk together the eggs, milk, dry mustard, garlic powder, salt, and pepper.
4. Soak it — Pour the egg mixture evenly over the bread, then press down gently so everything is submerged. Cover and refrigerate for at least 8 hours, or overnight.
5. Rest, then bake — Let the dish sit out for 20-30 minutes while the oven preheats to 350°F (175°C), then bake uncovered for 45-55 minutes.
6. Check for doneness — The center should be set, not jiggly, and the top should be golden brown. A knife inserted near the center should come out clean.
7. Rest and serve — Let it sit for 10 minutes before slicing so it holds together when served.

Substitutions Worth Knowing

• Bread swap: any sturdy, slightly stale bread works — French bread, sourdough, or even English muffins cut into pieces. Very soft sandwich bread will give a mushier result.
• Sausage swap: ground turkey or chicken sausage both work; they're leaner, so the casserole will be a bit less rich but still holds together fine.
• Dairy-free milk: unsweetened oat or soy milk can replace the whole milk, though the custard will be slightly less rich and may set a touch softer.
• Vegetarian version: skip the sausage and add sautéed mushrooms, spinach, or bell peppers instead — just make sure any vegetables are cooked and excess moisture drained first, or the extra liquid will keep the center from setting properly.

Troubleshooting

The center is still wobbly after the full bake time. This usually means the dish went into the oven cold, straight from the fridge — a cold casserole needs noticeably longer to bake through. Give it another 10-15 minutes, tenting the top loosely with foil if it's already browned enough.

It came out watery or soggy. This is almost always a bread issue — using fresh, very soft bread instead of day-old bread means it can't fully absorb the custard, so the extra liquid pools at the bottom.

Storage, Reheating, and Freezing

• Fridge: cover and store leftovers for up to 4 days.
• Reheat: individual slices reheat well in the microwave (60-90 seconds), or in a 325°F oven for about 15 minutes for a firmer texture.
• Freezer: this casserole freezes well after baking — cool completely, wrap tightly, and freeze for up to 2 months. Thaw overnight in the fridge before reheating in the oven.

Serving Suggestions

This casserole is filling enough on its own, but it pairs well with fresh fruit, a simple green salad, or Crispy Diner-Style Hash Browns on the side for a full spread. Hot sauce or salsa on top adds a nice kick if you like things spicier.