Overnight Breakfast Casserole Bake

This hearty overnight breakfast casserole has transformed my family's morning routine, especially during busy holidays when time is precious but a delicious breakfast is non-negotiable.

I first made this casserole when hosting my in-laws for Christmas morning. The ability to prepare everything the night before meant I could enjoy coffee and present-opening instead of being stuck in the kitchen while everyone else had fun.

Ingredients

• Day-old bread cubes: 6 cups allows the bread to better absorb the egg mixture without becoming soggy; choose a hearty variety like sourdough or French bread
• Breakfast sausage: 1 lb provides savory protein foundation; opt for sage-flavored for extra flavor dimension
• Cheddar cheese: 1 cup delivers classic sharp flavor; freshly shredded melts much better than pre-shredded bags
• Mozzarella cheese: 1/2 cup creates that perfect gooey stretch factor; use whole milk mozzarella for richest results
• Green onions: 1/4 cup adds fresh bite and color without overpowering; look for firm stalks with vibrant green tops
• Eggs: 8 large provides structure and richness; room temperature eggs blend more easily
• Milk: 2 cups creates custard-like texture; whole milk produces the creamiest result
• Garlic powder: 1/2 teaspoon adds depth without texture; fresh garlic would provide
• Onion powder: 1/2 teaspoon gives aromatic quality without chunks; choose a quality brand for best flavor
• Salt and pepper to taste: enhances all other flavors; sea salt and freshly ground pepper make a difference
• Butter or cooking spray: prevents sticking; real butter adds subtle flavor

Step-by-Step Instructions

Prepare baking dish:

Generously apply butter or cooking spray to your 9x13 baking dish, ensuring complete coverage including corners and sides. This crucial step prevents any sticking and makes serving much easier later.

Arrange bread foundation:

Spread the cubed bread in an even layer across the bottom of your buttered dish. Slightly pressing down helps create a more uniform base, but avoid compacting too much as you want some texture and space for the egg mixture to infiltrate.

Cook breakfast meat:

Brown the sausage in a skillet over medium heat, breaking it into small crumbles with a wooden spoon. Cook thoroughly until no pink remains, about 7-8 minutes. Transfer to a paper towel-lined plate to drain excess fat, which prevents a greasy casserole.

Layer proteins and cheeses:

Distribute the cooked sausage evenly over the bread cubes, ensuring coverage across the entire dish. Follow with an even layer of the cheddar cheese, then the mozzarella, and finally the green onions if using. This layering approach creates distinct flavor pockets throughout the casserole.

Create egg mixture:

In a large bowl, crack all 8 eggs and whisk until yolks and whites are fully incorporated. Pour in the milk while continuing to whisk, then add garlic powder, onion powder, salt, and pepper. Whisk vigorously until the mixture is completely homogeneous with no streaks of egg white visible.

Combine components:

Slowly pour the egg mixture over the layered ingredients, starting at the edges and moving inward. Gently press down on any floating bread pieces to ensure they begin absorbing the liquid. The egg mixture should just barely reach the top layer of ingredients without overflowing.

Refrigerate overnight:

Cover the casserole tightly with plastic wrap or aluminum foil, pressing it directly onto the surface to prevent air exposure. Refrigerate for at least 6 hours or ideally overnight, allowing time for the bread to fully absorb the egg mixture and for flavors to meld together.

Bake to perfection:

Remove the casserole from the refrigerator while preheating your oven to 350°F. Remove the covering and bake uncovered for 45-55 minutes. The casserole is done when the center is completely set with no jiggling when gently shaken, and the top has turned a beautiful golden brown.

Rest before serving:

Allow the finished casserole to rest for 10 minutes after removing from the oven. This resting period allows the internal structure to set fully, making for cleaner slices and preventing a runny texture. The casserole will remain hot even after this short rest.

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My absolute favorite way to enjoy this casserole is with a dollop of sour cream and a few dashes of hot sauce on top. The cool creaminess against the warm, savory casserole creates the perfect balance. My husband claims this dish saved our Christmas morning tradition after years of chaotic breakfast preparations.

Make It Your Own

This breakfast casserole welcomes endless customization based on your family's preferences. For a southwestern twist, substitute pepper jack cheese for the cheddar and add a can of drained green chiles. Vegetarians can skip the meat entirely and double up on vegetables like sautéed bell peppers, spinach, and mushrooms. For an extra decadent version, try using half and half instead of milk and adding a layer of cream cheese chunks before baking.

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Perfect Pairings

A vibrant fruit salad makes the ideal companion to this rich casserole, providing refreshing contrast to the savory flavors. For a complete brunch spread, serve alongside mimosas and a simple green salad dressed with light vinaigrette. If serving for a special occasion, consider offering small ramekins of maple syrup for drizzling—the sweet and savory combination is surprisingly delightful.

Troubleshooting Tips

If your casserole seems too dry after baking, you likely need more liquid in your egg mixture. Next time, try increasing the milk by 1/4 cup. Conversely, if your casserole is too soggy, your bread might be too fresh. Either use day-old bread or quickly toast fresh bread cubes in the oven before assembling. For more even baking, rotate your casserole halfway through the cooking time, especially if your oven has hot spots.

Frequently Asked Questions

→ Can I use different types of meat?

Yes! You can substitute sausage with ham, bacon, or any of your favorite breakfast meats.

→ Do I have to refrigerate it overnight?

Refrigerating allows the bread to soak up the egg mixture, but you can shorten the rest time to 2–4 hours if needed.

→ Can I make this dairy-free?

Absolutely! Use dairy-free cheese alternatives and a plant-based milk for a delicious result.

→ How can I prevent it from drying out?

Cover the casserole with foil during baking or ensure the egg mixture fully soaks the bread before baking.

→ What can I serve with this dish?

Pair it with fresh fruit, a side of yogurt, or a light salad for a balanced breakfast or brunch.