Can I make this casserole without the bread layer?

Absolutely! The bread adds nice texture and helps absorb moisture, but you can omit it for a more frittata-like dish. Alternatively, substitute frozen hash browns (about 3 cups) for a gluten-free option with a different but equally delicious texture.

Why is my breakfast casserole watery?

This typically happens when vegetables release too much moisture during baking. Make sure to pre-cook vegetables thoroughly and drain any excess liquid before adding them to the casserole. Also, using stale or toasted bread helps absorb moisture better than fresh bread.

Can I use egg whites or an egg substitute instead of whole eggs?

Yes, though the texture and richness will be different. For a lower-cholesterol version, substitute half the eggs with egg whites (2 whites = 1 whole egg). Commercial egg substitutes also work following package conversion guidelines, but expect a lighter final dish.

How do I know when the casserole is fully cooked?

The casserole should be golden brown on top with crispy edges. The center should be set but might have a slight jiggle - similar to a cheesecake. A toothpick inserted in the center should come out clean without wet egg mixture. If the top browns too quickly before the center is done, cover loosely with foil for the remaining bake time.

Easy Make-Ahead Breakfast Casserole Recipe

Description

This Easy Make-Ahead Breakfast Casserole is a hearty and customizable dish perfect for feeding a crowd or meal prepping for the week. Packed with crusty bread, flavorful sausage, vibrant vegetables, and melty cheese, it’s the ultimate comfort breakfast. The best part? You can assemble everything the day before, making mornings stress-free while still enjoying a warm, home-cooked meal. Serve this versatile dish plain or pair it with your favorite sides for a complete start to your day.

Ingredients

Units Scale

Bread Base

4 cups (175g or 6 oz) cubes of crusty bread

Sausage and Vegetables

1 teaspoon olive oil
1 pound ground pork sausage, casings removed
1 teaspoon dried rosemary or Italian seasoning (optional)
3/4 cup (100g) chopped yellow onion (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

Egg Mixture

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 onions and/or chopped parsley

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Instructions

Prepare the Baking Dish
Grease a 9×13-inch or any 3–4-quart oven-safe dish. Evenly layer the bread cubes across the bottom of the pan as the casserole’s base.
Cook the Sausage and Vegetables
Heat olive oil in a large skillet over medium heat. Add the ground sausage and optional rosemary or Italian seasoning. Break the sausage into bite-size pieces using a wooden spoon or spatula as it cooks. Add the onion, garlic, bell peppers, mushrooms, and spinach to the skillet, and cook until the vegetables are slightly softened and the sausage is mostly cooked through—about 5–6 minutes. Remove the skillet from heat and spread the mixture evenly over the bread cubes in the baking dish.
Whisk the Egg Mixture
In a mixing bowl, whisk together the eggs, salt, pepper, milk or half-and-half, and shredded cheddar cheese. Pour this mixture evenly over the sausage and vegetable layer in the baking dish. Sprinkle a bit more salt and pepper on top, if desired.
Refrigerate the Casserole
Cover the casserole with plastic wrap or aluminum foil and refrigerate for at least 30 minutes or up to 24 hours for maximum convenience. When ready to bake, allow the casserole to sit at room temperature for 10–15 minutes while preheating the oven.
Bake the Casserole
Preheat the oven to 375°F (191°C). Bake the uncovered casserole until the top is golden, the edges are crisp, and a toothpick inserted into the center comes out clean—approximately 40–45 minutes.
Cool, Serve, and Enjoy
Let the baked casserole cool for about 10 minutes before slicing and serving. Garnish with green onions and parsley for added flavor and color.
Storing Leftovers
Leftovers can be stored in the refrigerator for up to 5 days. Reheat individual portions in the microwave.

Notes

Make-Ahead: You can prepare and assemble the casserole up to 24 hours in advance. For best results, cover and refrigerate until ready to bake.
Freezing: The casserole can be frozen pre-baked or post-baked for up to 3 months. If freezing after assembly, cover with plastic wrap and foil before freezing. Thaw overnight in the fridge and bake as directed. For freezing after baking, allow it to cool completely, then wrap and freeze. Thaw overnight and reheat in a 350°F (177°C) oven for 25–30 minutes.
Bread Tips: Use crusty bread such as sourdough or French bread. If bread is fresh, toast it in a 300°F (149°C) oven for 10 minutes to firm it up before using.
Substitutions: Sausage can be replaced with turkey, beef, chicken, bacon, or ham. Vegetables like broccoli, zucchini, or kale can be added or substituted based on preference.
Vegetarian Option: Omit the meat and substitute with an additional cup of vegetables.
Dairy-Free: Use a dairy-free milk alternative and skip or replace cheese with a dairy-free option.

Nutrition

Serving Size: 1 slice
Calories: 220kcal
Sugar: 3g
Sodium: 450mg
Fat: 14g
Saturated Fat: 6g
Unsaturated Fat: 8g
Trans Fat: 0g
Carbohydrates: 10g
Fiber: 1g
Protein: 13g
Cholesterol: 185mg