This Easy Make-Ahead Breakfast Casserole is the perfect solution for a delicious, stress-free morning meal. Loaded with savory sausage, eggs, veggies, and melty cheddar cheese, all baked together with crusty bread, this casserole offers the comfort of a hearty breakfast without the hassle of cooking each item separately. It’s an ideal dish for busy mornings, brunches, or family gatherings. Plus, it can be prepared the night before and baked in the morning, making it a real time-saver!

Why You’ll Love This Recipe

This breakfast casserole is a complete meal in one dish, packed with flavor and nutrients. The bread absorbs the egg mixture, creating a rich and satisfying base, while the sausage, vegetables, and cheese elevate the flavor profile. The best part is that you can prepare it ahead of time, allowing the flavors to meld together overnight, making it even more delicious when you bake it the next day. Whether you’re feeding a crowd or preparing breakfast for the week, this casserole is a winner.

Ingredients

4 cups (175g or 6 oz) cubes of crusty bread
1 teaspoon olive oil
1 teaspoon dried rosemary or Italian seasoning, optional
3/4 cup (100g) chopped yellow onion (about 1/2 of a large onion)
2 garlic cloves, minced
2 cups (275g or 9-10 oz) chopped bell peppers
1 cup (100g or 3 oz) sliced mushrooms
1 cup roughly chopped fresh spinach
12 large eggs
1/4 teaspoon salt
1/8 teaspoon freshly ground black pepper
2/3 cup (160ml) milk or half-and-half
1 cup (100g or 3.5 oz) shredded cheddar cheese
Optional garnish: green onion and/or chopped parsley

(Tip: You’ll find the full list of ingredients and measurements in the recipe card below.)

Directions

Step 1: Prepare the Casserole Dish

Grease a 9×13-inch or any 3–4-quart oven-safe dish. Arrange the bread cubes in an even layer at the bottom of the pan.

Step 2: Cook the Sausage and Vegetables

Heat olive oil in a large skillet over medium heat. Add the sausage and rosemary or Italian seasoning, if using. Break up the sausage into bite-sized pieces as it begins to cook. Once the sausage is nearly cooked through, add the onion, garlic, bell peppers, mushrooms, and spinach. Cook for about 5–6 minutes, or until the vegetables have softened slightly, and the sausage is mostly cooked through.

Remove from heat and spread the sausage-vegetable mixture evenly on top of the bread cubes.

Step 3: Prepare the Egg Mixture

In a bowl, whisk together the eggs, salt, pepper, milk (or half-and-half), and shredded cheddar cheese until well combined. Pour the egg mixture evenly over the sausage and vegetable mixture in the casserole dish. Add a little more salt and pepper to the top for extra seasoning.

Step 4: Refrigerate the Casserole

Cover the casserole with plastic wrap or aluminum foil and refrigerate for at least 30 minutes, or up to 24 hours. When ready to bake, allow it to sit at room temperature for 10–15 minutes while the oven preheats.

Step 5: Bake the Casserole

Preheat your oven to 375°F (191°C). Uncover the casserole and bake it for 40–45 minutes, or until the top is golden, the edges are crisp, and a toothpick inserted in the center comes out clean.

Step 6: Serve

Cool the casserole for about 10 minutes, then slice and serve. Garnish with green onions or chopped parsley, if desired.

Servings and Timing

Servings: Makes about 8 servings
Preparation Time: 20 minutes
Cooking Time: 40–45 minutes
Total Time: 1 hour (including resting time before baking)

Variations

Add More Protein: For an extra protein boost, add cooked bacon or turkey sausage to the casserole.
Vegetarian Version: Skip the sausage and add more vegetables like zucchini, tomatoes, or broccoli for a fully vegetarian option.
Spicy Kick: Add a chopped jalapeño or a dash of hot sauce to the egg mixture for a spicy twist.
Cheese Options: Experiment with different cheeses like mozzarella, pepper jack, or feta to change the flavor profile.

Storage/Reheating

Storage: Leftover casserole can be stored in an airtight container in the refrigerator for up to 5 days.
Reheating: Reheat individual portions in the microwave, or heat the whole casserole in the oven at 350°F (175°C) for about 10–15 minutes until warmed through.

FAQs

1. Can I make this casserole without sausage?

Yes, you can omit the sausage or replace it with bacon, turkey sausage, or a meatless alternative like tofu crumbles.

2. Can I use frozen vegetables instead of fresh ones?

Yes, you can use frozen bell peppers and mushrooms, but make sure to thaw and drain any excess water before adding them to the casserole.

3. Can I make this casserole dairy-free?

Yes, substitute the milk or half-and-half with a dairy-free alternative, such as almond milk or oat milk, and use a dairy-free cheese alternative.

4. Can I use a different type of bread?

Yes, you can use any type of crusty bread, such as sourdough, whole wheat, or baguette. Just ensure it’s sturdy enough to absorb the egg mixture without becoming too soggy.

5. Can I prepare this casserole ahead of time?

Yes, this casserole is perfect for making ahead. You can refrigerate it overnight or up to 24 hours before baking.

6. Can I freeze the casserole?

Yes, you can freeze the unbaked casserole for up to 3 months. When ready to bake, thaw it overnight in the refrigerator and bake according to the instructions.

7. Can I add more cheese to the casserole?

Absolutely! If you love cheese, feel free to add extra cheese to the casserole before baking, or top it with cheese during the last 5 minutes of baking for a cheesy crust.

8. How can I make this casserole spicier?

To make it spicier, you can add chopped jalapeños, red pepper flakes, or hot sauce to the egg mixture before baking.

9. Can I skip the bread?

Yes, you can skip the bread for a lower-carb version. Consider adding more vegetables or using cauliflower rice as a base.

10. How do I know when the casserole is fully cooked?

The casserole is done when the top is golden and the edges are crisp. Insert a toothpick into the center — if it comes out clean, the casserole is cooked through.

Conclusion

This Easy Make-Ahead Breakfast Casserole is a fantastic, no-fuss option for a hearty breakfast or brunch. Packed with savory sausage, eggs, vegetables, and cheese, it’s a satisfying dish that can be prepared the night before for added convenience. With plenty of room for customization, this casserole is sure to become a family favorite for busy mornings or special gatherings.