Vegetable Egg Casserole

This vegetable egg casserole is a hearty baked breakfast made with eggs, hash browns, bell peppers, mushrooms, onions, and melted mozzarella and cheddar cheese. Perfect for brunch, meal prep, or feeding a crowd, this easy egg casserole recipe can be prepared ahead and baked in the oven for a warm, filling dish. A popular make-ahead breakfast casserole that works well for holidays, family gatherings, and busy mornings.

Ingredients

• 2 tablespoons extra-virgin olive oil, divided
• 16 oz mushrooms, sliced
• Salt and freshly ground black pepper, to taste
• 2 bell peppers (any color), seeded and chopped
• 1 yellow or white onion, chopped
• 12 large eggs
• 1/2 cup milk (any kind)
• 30 oz frozen shredded hash browns, thawed
• 12 oz shredded mozzarella cheese, divided
• 12 oz shredded cheddar cheese, divided

Instructions

1. Preheat the oven to 350°F (180°C). Lightly grease an 11×17-inch baking dish, or two medium baking dishes, with nonstick spray. Set aside.
2. Heat 1 tablespoon olive oil in a very large skillet over medium heat. Add the mushrooms and sauté until they release their liquid and it has fully evaporated. Season with salt and pepper, then continue cooking until the mushrooms are golden and tender. Transfer to a bowl and set aside.
3. Add the remaining tablespoon of olive oil to the same skillet. Add the chopped bell peppers and onion, season with salt and pepper, and sauté until crisp-tender. Lower the heat or add a small drizzle of oil if the vegetables begin to brown too quickly. Spread the vegetables on a plate and let cool slightly.
4. In a very large mixing bowl, whisk together the eggs, milk, salt, and pepper (about 3/4 teaspoon salt).
5. Add the hash browns, 8 oz mozzarella, and 8 oz cheddar to the egg mixture and stir until well combined. Fold in the sautéed mushrooms, peppers, and onions.
6. Pour the mixture into the prepared baking dish. Sprinkle the remaining cheeses evenly over the top. Cover loosely with nonstick-sprayed foil.
7. Bake for 50–60 minutes, or until the center is set. Remove the foil and bake for an additional 2–3 minutes, until the cheese is fully melted. If using two smaller dishes, begin checking for doneness at around 40 minutes.
8. Let the casserole rest for 10 minutes before slicing and serving.

---

Tips

• Let the sautéed vegetables cool slightly to prevent scrambling the eggs when mixed.
• Use a deep baking dish to avoid overflow as the casserole rises while baking.
• For cleaner slices, allow the casserole to rest before cutting.

Variations and Substitutions

• Replace mozzarella with Monterey Jack or Swiss cheese.
• Add spinach, zucchini, or broccoli for extra vegetables.
• Use dairy-free milk and cheese alternatives if needed.

FAQs

Can this be made ahead of time?
Yes, assemble the casserole, cover, and refrigerate overnight. Bake as directed the next day.

Can I freeze it?
Yes, bake fully, cool, then freeze in portions. Reheat in the oven until warmed through.

How do I know it’s done?
The center should be firm and no longer jiggly when gently shaken.

Serving Suggestions

• Serve with a fresh green salad or sliced fruit.
• Pair with toast, biscuits, or breakfast potatoes.
• Ideal for brunch gatherings or meal prep breakfasts.

Why You’ll Love This Recipe

• Hearty, filling, and packed with vegetables.
• Easy to prepare for feeding a crowd.
• Versatile recipe that works for breakfast, brunch, or dinner.