Overnight Breakfast Casserole Recipe for Busy Weeknights

Overnight breakfast casserole is the best thing I make when I know the morning will be rushed. I layer everything in a pan the night before and slide it into the oven the next day. This version uses breakfast sausage, sharp cheddar, and thick-cut bread soaked in a seasoned egg custard.

Why This Overnight Breakfast Casserole Works

The overnight soak is the secret. The bread absorbs the egg and milk mixture and bakes up custardy in the center with golden edges. No soggy bottom, no dry spots — just one cohesive baked layer.

Breakfast sausage gives every bite a savory, meaty bite. Sharp cheddar melts into the egg layer and browns slightly on top. This overnight breakfast casserole is exactly what a holiday morning needs without any scrambling at 7am.

Eight servings come out of one 9×13 pan. It feeds a crowd and reheats well all week.

Ingredients

• 1 lb breakfast sausage
• 6 large eggs
• 2 cups whole milk
• 1/2 cup sour cream
• 6 thick slices white bread, cubed (about 4 cups)
• 2 cups sharp cheddar cheese, shredded
• 1/2 teaspoon garlic powder
• 1/2 teaspoon onion powder
• 1/2 teaspoon dry mustard
• Salt and black pepper to taste

What You Need for Overnight Breakfast Casserole

Breakfast sausage — crumbled and cooked the night before. I use bulk pork sausage for the best browning. Turkey sausage works as a lighter option with the same flavor profile.

Thick-cut white bread — day-old bread soaks up more of the egg mixture and holds its structure better. Brioche or Texas toast both work well here and add a richer finish.

Sharp cheddar — pre-shredded is fine. The sharper the cheddar, the more pronounced the cheese flavor in the final bake. Mild cheddar works but fades into the background.

Sour cream — this adds tang to the egg custard and keeps the casserole moist. You can swap it for cream cheese softened and beaten smooth for a slightly richer texture.

Dry mustard — a small amount adds depth to the egg layer without a sharp mustard taste. This is a traditional strata seasoning that works in the background.

How to Make Overnight Breakfast Casserole

1. Cook the breakfast sausage in a skillet over medium heat, breaking it into crumbles. Drain excess fat and set aside to cool.
2. Cube the bread into 1-inch pieces and spread them in an even layer in a greased 9×13 baking dish.
3. Scatter the cooked sausage over the bread layer evenly.
4. Whisk together eggs, milk, sour cream, garlic powder, onion powder, dry mustard, salt, and pepper in a large bowl until smooth.
5. Pour the egg mixture evenly over the bread and sausage.
6. Sprinkle shredded cheddar over the top.
7. Cover the dish with plastic wrap and refrigerate for at least 3 hours or overnight.
8. The next morning, remove the dish from the fridge 30 minutes before baking.
9. Preheat the oven to 350°F (175°C).
10. Bake uncovered for 45 to 50 minutes until the center is set and the top is golden brown.
11. Let stand for 5 minutes before cutting and serving.

Overnight Breakfast Casserole Variations

Hashbrown Breakfast Casserole

Swap the bread for 3 cups of frozen hashbrowns. Press them into the bottom of the greased pan as your base layer. The hashbrowns crisp up along the bottom edges and add a satisfying potato bite instead of the strata texture.

Vegetarian Overnight Breakfast Casserole

Replace the sausage with diced bell peppers, mushrooms, and spinach sautéed in olive oil. The vegetables release moisture during cooking, so pat them dry before adding to keep the casserole from getting watery.

Sausage and Green Chile Breakfast Casserole

Add one 4 oz can of diced green chiles to the egg mixture before pouring it over the bread. Top with Pepper Jack instead of cheddar. This version leans toward Southwestern flavors and pairs well with hot sauce at the table.

Make-Ahead Individual Portions

Layer everything into greased muffin tins instead of a 9×13 pan. Refrigerate overnight, then bake at 350°F for 20 to 25 minutes. Each cup pops out cleanly and reheats from the fridge in 60 seconds.

Tips for the Best Overnight Breakfast Casserole

• I always use day-old or slightly stale bread. Fresh bread can turn mushy at the bottom if it absorbs too much egg mixture.
• Soak for at least 3 hours. Overnight gives the best result — the bread fully absorbs the custard and bakes up custardy all the way through.
• Pull the pan from the fridge 30 minutes before baking. A cold pan going straight into a hot oven can crack ceramic baking dishes and affects the bake time.
• The casserole is done when a knife inserted into the center comes out clean. If the top browns too fast, tent it with foil for the last 10 minutes.
• This overnight breakfast casserole doubles to a full sheet pan for a larger crowd. Double every ingredient and add 10 to 15 minutes to the bake time.

Make Ahead & Storage

The whole point of this overnight breakfast casserole is the make-ahead step. Assemble it up to 24 hours before baking. The longer it soaks, the better the custard texture in the center.

Leftovers keep in the fridge for 4 days covered tightly. Reheat individual slices in the microwave for 90 seconds or in a 325°F oven for 10 minutes. To freeze, cut the baked casserole into portions, wrap each piece in plastic wrap, and freeze for up to 2 months. Thaw overnight in the fridge before reheating.

Common Questions

Can I bake overnight breakfast casserole immediately without refrigerating?

Yes, but let the assembled casserole rest for at least 30 minutes so the bread absorbs some of the egg mixture before baking. The texture will be less custardy than the overnight version. Bake at 350°F for 45 to 50 minutes the same way.

How do I know when the overnight breakfast casserole is done?

Insert a knife into the center — it should come out clean with no runny egg. The top should be golden brown and slightly puffed. It will settle as it rests out of the oven.

Can I freeze overnight breakfast casserole before baking?

I recommend freezing it after baking, not before. The raw egg mixture can separate during freezing and the bread texture gets spongy. Bake it first, then freeze individual portions for up to 2 months.

What bread works best in overnight breakfast casserole?

Day-old white bread, brioche, or Texas toast. French bread also works well. Avoid thin sandwich bread — it turns too soft and dissolves into the egg layer instead of holding its shape.

This overnight breakfast casserole is the recipe I bring to every holiday breakfast and brunch. Save this recipe and tap the link for the full step-by-step guide at MillennialHawk.com.