12x18 Breakfast Casserole Recipe for Easy Morning Feasts

Start your day with this hearty and versatile 12×18 breakfast casserole, perfect for feeding a crowd or preparing ahead for busy mornings. Its combination of eggs, cheese, meats, and vegetables creates a satisfying meal that can be assembled the night before and baked fresh in the morning, saving you time without sacrificing flavor.

Ingredients

1 lb (450g) breakfast sausage or cooked bacon, crumbled or chopped
1 medium onion, diced
1 red bell pepper, diced
2 cups (200g) shredded cheddar cheese
8 large eggs
2 cups (480ml) milk (whole or 2%)
1 teaspoon salt
1/2 teaspoon black pepper
1 teaspoon dried oregano or thyme (optional)
4 cups (about 250g) cubed bread or bread cubes (day-old or toasted)

Butter or non-stick spray for greasing

Instructions

Preheat your oven to 350°F (175°C). Grease a 12×18-inch baking dish with butter or non-stick spray to prevent sticking.
In a skillet over medium heat, cook the sausage until browned and cooked through, about 8-10 minutes. Remove excess fat if necessary. If using bacon, cook until crispy, then chop into pieces.
In the same skillet, sauté the diced onion and bell pepper until softened, about 5 minutes. Add to the cooked sausage and stir to combine.

Spread the bread cubes evenly across the prepared baking dish. Layer the cooked sausage and vegetable mixture over the bread.
Sprinkle the shredded cheddar cheese evenly over the top of the sausage and vegetables.
In a large mixing bowl, whisk together the eggs, milk, salt, pepper, and herbs until well combined.

Pour the egg mixture evenly over the layers in the baking dish, ensuring all bread cubes are soaked. Gently press down on the bread to help it absorb the liquid.
Cover the dish with plastic wrap or foil and refrigerate for at least 2 hours or preferably overnight. This allows the flavors to meld and the bread to soak up the custard.
When ready to bake, remove from the fridge and let sit at room temperature for about 15 minutes. Bake uncovered in the preheated oven for 40-45 minutes, or until the casserole is puffed, golden, and a toothpick inserted in the center comes out clean.

Allow the casserole to rest for 5-10 minutes before serving. Slice into squares and enjoy!

Tips

Substitutions: Swap sausage for cooked ham, turkey bacon, or vegetarian sausage for different flavors. Use different cheeses like Monterey Jack or pepper jack for variety.
Storage: This casserole can be prepared a day in advance. Keep it refrigerated and bake it straight from the fridge, adding an extra 10 minutes to the baking time if cold.

Common mistakes: Ensure the bread is soaked well in the egg mixture; otherwise, parts may be dry. Avoid overbaking, which can make the casserole rubbery.
Additional toppings: Garnish with chopped chives, green onions, or fresh herbs before serving for added flavor and color.

Serving Suggestions

Serve this hearty breakfast casserole with fresh fruit, a side of crispy breakfast potatoes, or a simple mixed greens salad. For a complete brunch, add some toasted bagels or muffins and your favorite breakfast beverages like coffee, tea, or fresh orange juice.

Variations

Vegetarian Version: Replace the sausage with sautéed mushrooms, spinach, and sun-dried tomatoes. Use vegetarian cheese options if desired.
Low-Carb Version: Use low-carb bread or omit bread altogether, increasing the egg and cheese ratio. Add extra vegetables for bulk.
Meat Lover’s Version: Incorporate cooked sausage links, ham, and crispy bacon for a protein-packed meal.

Spicy Kick: Add diced jalapeños or hot sauce to the egg mixture for a spicy variation.

Storage and Reheating

This casserole keeps well for up to 3 days in the refrigerator. To reheat, cut into individual portions and microwave on high for 1-2 minutes, or until heated through. For best results, reheat in the oven at 350°F (175°C) for 10-15 minutes, covered with foil to prevent drying out. You can also freeze individual servings for up to 2 months; thaw overnight in the fridge and reheat as above.

Frequently Asked Questions

Can I prepare this casserole the night before?

Absolutely! Assemble the casserole, cover tightly, and refrigerate overnight. Baking it in the morning will give it time to absorb the flavors and make your morning stress-free.

Can I use frozen bread instead of fresh?

Yes, using day-old or frozen bread is actually preferable as it absorbs the custard better without becoming too soggy. Toasting the bread slightly before assembly can also help.

What if I don’t have a 12×18-inch dish?

You can use a slightly smaller or larger dish, but adjust the baking time accordingly. A 9×13-inch dish will work, but the casserole may be thicker and require a few extra minutes to bake thoroughly.

Is there a way to make this gluten-free?

Yes, substitute the bread with gluten-free bread or use cooked quinoa or cauliflower rice as a base. Just ensure the other ingredients, like sausage and cheese, are gluten-free.

How can I make this dish more kid-friendly?

Use milder cheeses and omit spicy ingredients. Also, add familiar flavors like hash browns or cooked breakfast sausage to appeal to children’s tastes.

12×18 Breakfast Casserole Recipe for Easy Morning Feasts