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Easy Egg Breakfast Casserole for a Protein-Packed Morning – Simple, Satisfying, and Make-Ahead Friendly

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Prep Time 10 minutes
Cook Time 35 minutes
Total Time 45 minutes
Servings 8 servings

Ingredients
  

  • 12 large eggs
  • 1 cup milk or unsweetened almond milk (or 3/4 cup milk + 1/4 cup plain Greek yogurt for extra protein)
  • 1 cup shredded cheese (cheddar, Monterey Jack, or mozzarella)
  • 1 cup cooked lean protein (turkey sausage, chicken sausage, turkey bacon, or crumbled tofu for vegetarian)
  • 2 cups vegetables, chopped (bell peppers, spinach, mushrooms, onions, or zucchini)
  • 1–2 tablespoons olive oil (for sautéing)
  • 1 teaspoon salt (adjust to taste)
  • 1/2 teaspoon black pepper
  • 1/2 teaspoon garlic powder (optional)
  • 1/2 teaspoon smoked paprika or chili powder (optional for a little warmth)
  • Fresh herbs like chives or parsley for garnish (optional)
  • Cooking spray or extra oil for the baking dish

Instructions
 

  • Prep the oven and pan: Preheat the oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish with cooking spray or oil.
  • Cook the add-ins: Warm olive oil in a skillet over medium heat. Sauté onions, peppers, and mushrooms until softened and most moisture evaporates, 5–7 minutes. Stir in spinach last so it wilts quickly. If using meat, cook it fully and drain excess fat.
  • Whisk the egg mixture: In a large bowl, whisk eggs, milk (and Greek yogurt if using), salt, pepper, garlic powder, and smoked paprika until smooth and slightly frothy.
  • Layer the casserole: Spread the cooked vegetables and protein evenly in the baking dish. Sprinkle half the cheese over the top. Pour the egg mixture evenly over everything. Finish with the remaining cheese.
  • Bake: Place on the center rack and bake 30–40 minutes, until the center is just set and a knife inserted near the middle comes out mostly clean. The top should be lightly golden.
  • Rest and slice: Let the casserole rest 5–10 minutes. This helps it set up so slices hold together. Garnish with chopped herbs, slice, and serve warm.