If mornings are busy, having breakfast ready to bake can make the day so much easier. This Easy Overnight Breakfast Casserole is prepared the night before, refrigerated overnight, and baked in the morning until golden, fluffy, and delicious. It is a comforting make-ahead breakfast that works beautifully for weekends, holidays, brunches, and family gatherings.

With hearty eggs, savory sausage, melty cheese, and bread soaked in a seasoned egg mixture, every bite is satisfying without requiring much morning prep. If you enjoy breakfast casseroles make ahead, this is one recipe worth keeping in your collection.

Table of Contents

Why You’ll Love This Overnight Breakfast Casserole

Make-ahead friendly: Assemble it the night before and bake it in the morning.
Simple ingredients: You only need a handful of everyday breakfast staples.
Great for gatherings: One casserole can feed a family or a small group.
Comforting and filling: Eggs, sausage, bread, and cheese make a satisfying combination.
Easy to customize: Add vegetables, switch the cheese, or use a different breakfast meat.
Perfect for busy mornings: Most of the preparation is finished the night before.

Ingredients

1 pound breakfast sausage
10 large eggs
2 cups whole milk
1 teaspoon Dijon mustard
1 teaspoon salt
½ teaspoon black pepper
½ teaspoon garlic powder
6 cups cubed day-old bread
2 cups shredded cheddar cheese
½ cup shredded Monterey Jack cheese
½ cup diced bell pepper
¼ cup finely diced onion
2 tablespoons chopped fresh parsley

How to Make Easy Overnight Breakfast Casserole

1. Cook the Sausage

Heat a large skillet over medium heat. Add the breakfast sausage and cook until browned and fully cooked, breaking it into small pieces as it cooks.

Drain any excess grease and set the sausage aside to cool slightly.

2. Prepare the Egg Mixture

In a large bowl, whisk together the eggs, milk, Dijon mustard, salt, black pepper, and garlic powder until well combined.

The mustard adds a subtle savory flavor without making the casserole taste strongly of mustard.

3. Assemble the Casserole

Lightly grease a 9 × 13-inch baking dish.

Spread the cubed bread evenly across the bottom. Sprinkle the cooked sausage, diced bell pepper, onion, cheddar cheese, and Monterey Jack cheese over the bread.

Pour the egg mixture evenly over everything. Gently press the bread down with a spatula so it absorbs the egg mixture.

Sprinkle the chopped parsley over the top.

4. Refrigerate Overnight

Cover the baking dish tightly with foil or plastic wrap and refrigerate for at least 6 hours, preferably overnight.

This resting time allows the bread to absorb the seasoned egg mixture, giving the casserole a soft, flavorful center when baked.

5. Bake

The next morning, remove the casserole from the refrigerator and let it sit at room temperature while the oven preheats.

Preheat the oven to 350°F (175°C).

Bake covered for about 30 minutes. Remove the cover and continue baking for another 20–25 minutes, or until the center is set and the top is golden brown.

Let the casserole rest for about 10 minutes before slicing.

Tips for the Best Overnight Breakfast Casserole

Use day-old bread

Slightly stale bread absorbs the egg mixture better than very fresh bread. French bread, sourdough, brioche, or sandwich bread can all work.

Don’t skip the overnight rest

The overnight refrigeration isn’t just for convenience. It gives the bread time to absorb the egg mixture and allows the flavors to develop.

Check the center before removing it

The casserole should be set in the middle rather than liquid or overly jiggly. If necessary, give it a few extra minutes in the oven.

Let it rest before serving

Allowing the casserole to sit for about 10 minutes makes it easier to cut into neat portions.

Variations

Vegetable Breakfast Casserole

Replace some or all of the sausage with sautéed spinach, mushrooms, tomatoes, broccoli, or additional bell peppers for a vegetable-forward option.

Ham and Cheese

Use diced cooked ham instead of sausage and pair it with cheddar, Swiss, or Monterey Jack cheese.

Spicy Version

Add diced jalapeño, red pepper flakes, or a little hot sauce to the egg mixture.

Different Cheese

Try mozzarella, pepper Jack, Gruyère, Swiss, or a combination of your favorite cheeses.

Storage Tips

This casserole is designed to be prepared ahead of time.

To refrigerate: Assemble the casserole, cover it, and refrigerate overnight before baking.

store leftovers: Cool completely and refrigerate in an airtight container for up to 3–4 days.

To reheat: Warm individual portions in the microwave or reheat larger portions in a covered baking dish at 325°F until heated through.

To freeze: For the best texture, freeze baked portions after they have cooled completely. Wrap well and freeze for up to 2 months. Thaw overnight in the refrigerator before reheating.

What to Serve with Breakfast Casserole

This casserole is filling on its own, but you can serve it with:

Fresh berries
Sliced melon
Orange or grapefruit
A simple green salad
Roasted potatoes
Fresh fruit salad
Coffee or fresh juice

Frequently Asked Questions

Can I prepare this casserole more than one night ahead?

Yes. You can assemble it up to about 24 hours before baking as long as it remains properly refrigerated.

Can I use fresh bread?

Yes, but day-old bread generally gives you a better texture because it absorbs the egg mixture without becoming overly soft.

Can I make it without sausage?

Absolutely. Leave out the sausage and add vegetables, cooked mushrooms, spinach, or another filling of your choice.

Can I use a different size baking dish?

Yes, but the baking time will vary. A deeper casserole may need additional time, while a larger, shallower dish may bake more quickly.

How do I know when it is done?

The center should be set, the eggs should no longer look wet, and the top should be lightly golden.

Conclusion

This Easy Overnight Breakfast Casserole is a practical choice when you want a warm, homemade breakfast without starting from scratch first thing in the morning. Assemble it the night before, let the refrigerator do the work, and simply bake it when you’re ready for breakfast.

Whether you’re planning a holiday brunch, feeding overnight guests, or looking for breakfast ideas to make ahead, this casserole gives you a hearty and comforting meal with very little morning effort.

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