Can I make this spinach and mushroom egg casserole ahead of time?

Yes! You can assemble the casserole up to 24 hours in advance , cover it tightly, and store it in the refrigerator until you’re ready to bake.

Do I need to let the casserole sit out before baking?

For best results, let the casserole sit at room temperature for about 15 minutes before baking. This helps it cook more evenly.

How long do leftovers last?

Leftovers store well in an airtight container in the refrigerator for up to 4 days , making this a great option for meal prep.

What should I serve with spinach and mushroom egg casserole?

Serve it with fresh fruit, toast, or roasted potatoes, and pancakes for the kids.

Is this casserole good for holidays or busy mornings?

Absolutely. This spinach and mushroom egg casserole proves that simple food can still feel special. Whether you’re planning a holiday brunch or need an easy weekday meal, this egg cheese spinach breakfast casserole delivers every time.

Is this casserole good for an everyday weeknight dinner?

Yes, absolutely. T his spinach and mushroom egg casserole is great for an everyday weeknight dinner. It’s filling, protein-packed, and loaded with vegetables, so it works just as well for dinner as it does for breakfast or brunch. Pair it with a simple side salad, and you’ve got a balanced, stress-free meal that comes together quickly. You do not have to make this the night before .

Make Ahead Spinach and Mushroom Egg Casserole

A healthy, make-ahead spinach and mushroom egg casserole made with fresh vegetables, eggs, and Swiss cheese. This easy breakfast casserole is perfect for brunch, holidays, or a simple weeknight dinner.

Total Time: 50 minutes
Yield: 8 servings 1x

Ingredients

Units Scale

1 tablespoon Olive Oil
1/2 large Onion, chopped
1 Red Bell Pepper, chopped
2 (8 oz) packages Fresh Mushrooms, sliced (about 4 cups)
1/4 teaspoon Salt
1/4 teaspoon Black Pepper
1/4 teaspoon Garlic Powder
4 cups Fresh Baby Spinach
10 large Eggs
3/4 cup Whole Milk or Half and Half
8 oz Swiss Cheese, shredded (about 3-4 cups)

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Instructions

Preheat your oven to 350°F and lightly grease a 13×9 baking dish.
Heat olive oil in a large skillet over medium heat.
Sauté the chopped onion and red bell pepper for about 2 minutes, until slightly softened.
Add sliced mushrooms, salt, pepper, and garlic powder. Cook for 2–4 minutes, until mushrooms release their moisture.
Add spinach and cook just until wilted. Remove from heat.
In a large bowl, whisk together the eggs and milk (or half and half).
Stir in the shredded Swiss cheese.
Fold the sautéed vegetables into the egg mixture.
Pour everything into the prepared baking dish.
Bake for 40 minutes, or until the center is set and the top is lightly golden.
Let the casserole rest for 5–10 minutes before slicing.

Author: Susan Buonpane
Prep Time: 10
Cook Time: 40
Category: Breakfast
Method: Baking
Cuisine: American