Cheesy Spinach & Mushroom Breakfast Casserole

Hi, I’m Sarah Jansen, a traveler and food blogger who finds joy in creating meals that bring comfort and convenience to busy mornings. One of my go-to recipes is this Cheesy Spinach & Mushroom Breakfast Casserole. It’s hearty, customizable, and perfect for serving a crowd—or making ahead for stress-free weekday breakfasts. With fluffy eggs, earthy mushrooms, vibrant spinach, and golden bubbly cheese, this dish feels both indulgent and nourishing. It’s the kind of breakfast that makes mornings brighter, whether you’re preparing for Sunday brunch or a cozy holiday gathering.

This Breakfast Casserole with Spinach and Mushrooms is the definition of wholesome comfort food. It combines sautéed vegetables, seasoned eggs, and melty cheese baked together into a golden casserole that’s equal parts hearty and satisfying. The beauty of this recipe lies in its versatility—you can prepare it ahead of time and reheat throughout the week, or serve it fresh from the oven for a brunch centerpiece. With its rich flavor, vibrant color, and cheesy appeal, it’s a recipe that feels special yet practical for everyday enjoyment.

Why This Recipe Works

Make-Ahead Friendly: Assemble the night before and bake in the morning.
Balanced Nutrition: Eggs for protein, spinach for vitamins, mushrooms for earthy richness.
Customizable: Easily add sausage, bacon, or extra veggies.
Family-Style Dish: Serves multiple people at once.
Comfort & Elegance: Cheesy and cozy, yet refined enough for brunch gatherings.

Health Benefits

Protein-Packed: Eggs provide sustained energy.
Iron & Vitamins: Spinach boosts immunity and supports healthy blood.
Low Carb: Naturally fits into low-carb lifestyles.
Bone Health: Cheese adds calcium for strength.
Antioxidants: Mushrooms contain selenium and immune-supporting nutrients.

Ingredients

10 large eggs
1 cup milk (whole or 2%)
1 tablespoon olive oil
2 cups fresh spinach, roughly chopped
1 ½ cups mushrooms, sliced
1 small onion, diced
2 garlic cloves, minced
1 ½ cups shredded cheddar cheese (or a mix of mozzarella and cheddar)
½ teaspoon salt
¼ teaspoon black pepper
¼ teaspoon nutmeg (optional, enhances spinach flavor)
Cooking spray or butter for greasing the dish

How to Make Cheesy Spinach & Mushroom Breakfast Casserole

Start by sautéing onions, garlic, mushrooms, and spinach in olive oil until softened. In a large bowl, whisk together eggs, milk, salt, pepper, and nutmeg. Grease a 9×13-inch baking dish with butter or cooking spray. Spread the sautéed vegetables evenly in the dish, then sprinkle with shredded cheese. Pour the egg mixture over the top, ensuring even coverage. Bake at 375°F (190°C) for 35–40 minutes, or until eggs are set and cheese is golden brown. Let cool for 5 minutes before slicing. Serve warm with toast, potatoes, or fresh fruit.

Instructions:

Preheat & Prepare: Begin by preheating your oven to 375°F (190°C). Grease a 9×13-inch casserole dish with butter or cooking spray to prevent sticking.
Sauté the Vegetables: In a large skillet, heat olive oil over medium heat. Add onions and garlic, cooking until fragrant, about 2 minutes. Stir in mushrooms and cook until softened and lightly browned, around 5 minutes. Add chopped spinach and cook until wilted, about 2 minutes. Remove from heat.
Whisk the Egg Mixture: In a large mixing bowl, whisk together the eggs, milk, salt, pepper, and nutmeg (if using). The nutmeg adds a subtle warmth that complements spinach beautifully.
Assemble the Casserole: Spread the sautéed vegetables evenly across the greased baking dish. Sprinkle shredded cheese over the vegetables, reserving a small handful for topping. Slowly pour the egg mixture over the vegetables and cheese, ensuring everything is well distributed. Top with the reserved cheese.
Bake the Casserole: Place the dish in the preheated oven and bake for 35–40 minutes. The casserole is done when the eggs are fully set and the top is golden brown. To test, insert a knife in the center—it should come out clean.
Rest & Serve: Remove the casserole from the oven and let it rest for 5 minutes before slicing. This helps it set further and makes cutting easier.
Enjoy: Serve slices warm with a side of toast, roasted potatoes, or a light salad.

This step-by-step approach ensures a casserole that’s fluffy, flavorful, and perfectly cheesy—ideal for breakfast, brunch, or meal prep.

Cook & Prep Times

Prep Time: 15 minutes
Cook Time: 35–40 minutes
Rest Time: 5 minutes
Total Time: 55 minutes

Nutrition Information (per serving, serves 6)

Calories: 280
Protein: 20g
Fat: 19g
Saturated Fat: 8g
Carbohydrates: 7g
Fiber: 1g
Sodium: 340mg

Serving with Cheesy Spinach & Mushroom Breakfast Casserole

This Spinach & Mushroom Breakfast Casserole is best served hot, straight from the oven, with its cheesy golden crust still bubbling. Pair with crispy roasted potatoes or a fresh fruit salad for a balanced meal. For brunch gatherings, serve alongside fresh pastries and coffee for a complete spread. The casserole slices beautifully, making it easy to serve family-style at the table. Leftovers reheat well, so you can enjoy it throughout the week. It’s the kind of versatile dish that’s equally at home on a busy weekday or festive holiday morning.

Pro Tips & Variations

Make Ahead: Assemble the casserole the night before and bake in the morning.
Protein Boost: Add cooked sausage, bacon, or ham.
Cheese Options: Swap cheddar for Swiss, feta, or mozzarella.
Vegetarian Twist: Add zucchini, bell peppers, or sun-dried tomatoes.
Lighter Version: Use skim milk and reduced-fat cheese.

The Bottom Line

The Cheesy Spinach & Mushroom Breakfast Casserole is a recipe that delivers on every front: comforting, versatile, and easy to make. It’s a dish that feels indulgent with its cheesy top layer, yet nourishing thanks to its protein and veggie-packed base. For me, it’s the kind of recipe that transforms mornings into something special, whether you’re rushing through a weekday or hosting a relaxed weekend brunch. With its make-ahead convenience and family-style appeal, it’s destined to become a breakfast favorite in your kitchen too.

Cheesy Spinach & Mushroom Breakfast Casserole – A Make-Ahead Morning Delight