Spinach Mushroom Breakfast Casserole

Featured in Start Your Day with Grace.

This spinach and mushroom breakfast casserole is a simple and delicious vegetarian dish perfect for mornings or brunch. Sautéed cremini mushrooms, wilted spinach, and garlic create a flavorful base, complemented by creamy goat cheese and fluffy eggs. Easy to prepare and ideal for servings up to 12, it’s a crowd-pleaser that balances wholesome ingredients with rich, breakfast-worthy textures. Serve warm and garnish with fresh chives for a finishing touch.

Barbara Chef
Updated on Tue, 29 Apr 2025 14:36:38 GMT
A dish of mushrooms and spinach. Pin it
A dish of mushrooms and spinach. | gracefulflavors.com

This hearty spinach mushroom breakfast casserole has been my weekend brunch solution for years. Packed with protein and veggies, it's become my go-to recipe whenever I host morning gatherings or need to meal prep for busy weekdays.

I first made this casserole when my in-laws visited unexpectedly one Sunday morning. Everyone raved about it, and now it's requested at every family gathering. The combination of earthy mushrooms and tangy goat cheese creates a flavor profile that even vegetable skeptics enjoy.

Ingredients

  • Olive oil: adds a subtle richness when sautéing the vegetables
  • Cremini mushrooms: provide meaty texture and umami flavor; choose firm ones with tight caps
  • Spinach leaves: fresh spinach wilts perfectly and provides essential nutrients
  • Garlic: fresh minced cloves offer more flavor than pre-minced varieties
  • Kosher salt and black pepper: essential for balancing and enhancing all flavors
  • Green onions: add a mild onion flavor without overpowering the dish
  • Goat cheese: creates pockets of creamy tanginess throughout the casserole
  • Large eggs: form the protein-rich base; look for pasture-raised for best flavor
  • Milk: helps create a custard-like texture; whole milk works best but any variety works
  • Fresh chives (optional): adds bright color and mild flavor as garnish

Step-by-Step Instructions

Prep Your Baking Dish:
Preheat oven to 350 degrees Fahrenheit and thoroughly grease a 9×13 inch baking dish with nonstick spray. Make sure to cover the corners and sides completely to prevent sticking since eggs tend to cling to ungreased surfaces.
Sauté The Vegetables:
Heat olive oil in a large skillet over high heat until shimmering. Add sliced mushrooms in a single layer if possible and cook undisturbed for about a minute before stirring. Continue cooking for about 2 more minutes until they release their moisture and become tender. Add spinach and minced garlic, then cook for another 3 minutes, stirring frequently until spinach is completely wilted but still bright green. Season mixture with salt and pepper to enhance the natural flavors.
Layer The Base:
Transfer the cooked vegetable mixture to your prepared baking dish, spreading it evenly across the bottom. Sprinkle the sliced green onions over the vegetables, distributing them uniformly. Take half of your goat cheese and crumble it over the vegetables in small pieces to ensure pockets of cheese throughout the casserole.
Prepare And Add Egg Mixture:
In a large bowl, crack 18 eggs and add the milk. Whisk vigorously until completely combined and slightly frothy. Season the egg mixture with salt and pepper. Pour this mixture slowly over the vegetable and cheese layer, allowing it to settle evenly. Crumble the remaining goat cheese over the top, creating an attractive pattern.
Bake To Perfection:
Place the casserole in the preheated oven and bake for 30 to 40 minutes. You'll know it's done when the eggs are completely set and the edges have a slight golden brown color. The center should be firm but still moist when lightly touched. Allow to rest for 5 minutes before garnishing with fresh chives and cutting into squares.
A dish with mushrooms and spinach. Pin it
A dish with mushrooms and spinach. | gracefulflavors.com

The cremini mushrooms are truly the star of this casserole. I discovered their rich flavor after years of using button mushrooms, and the difference is remarkable. When my daughter was younger, she would pick them out, but now she requests extra mushrooms whenever I make this dish for our Sunday brunches.

Make Ahead Magic

This casserole excels as a make-ahead option. You can prepare the entire casserole up to the baking step, cover tightly with plastic wrap, and refrigerate overnight. When ready to serve, remove from the refrigerator 30 minutes before baking to take the chill off, then bake as directed, adding about 5 extra minutes to the cooking time. For busy holiday mornings or when hosting brunch, this time-saving technique is invaluable.

Storage Solutions

Once cooled, leftover casserole can be refrigerated for up to 4 days in an airtight container. For individual portions, cut the casserole into squares and store them separately for grab-and-go breakfasts during the week. To reheat, microwave individual portions for about 60 seconds or warm in a 325°F oven until heated through. This casserole also freezes beautifully for up to 3 months; wrap individual pieces tightly in plastic wrap, then foil, and defrost overnight in the refrigerator before reheating.

Clever Substitutions

This recipe welcomes adaptations based on what you have available. Swiss chard or kale can replace spinach; use the same amount but remove tough stems first. Feta cheese creates a saltier profile than goat cheese, while cream cheese offers a milder flavor. Any variety of mushrooms works wonderfully—portobello, shiitake, or white button mushrooms all bring their unique character to the dish. For a dairy-free version, substitute unsweetened almond milk and omit the cheese or use a plant-based alternative.

A dish of mushrooms and spinach. Pin it
A dish of mushrooms and spinach. | gracefulflavors.com

Serving Suggestions

This casserole pairs beautifully with a variety of sides. Serve with toasted sourdough bread and fresh fruit for a complete breakfast spread. For brunch gatherings, offer it alongside a simple arugula salad dressed with lemon vinaigrette to cut through the richness. During cooler months, a side of roasted breakfast potatoes complements the casserole perfectly. For a lighter option, serve smaller portions with avocado slices and fresh tomatoes drizzled with olive oil.

Frequently Asked Questions

→ Can I use other types of mushrooms?

Yes, you can substitute cremini mushrooms with button mushrooms, shiitake, or portobello for a slightly different flavor.

→ How can I make this casserole dairy-free?

To make it dairy-free, replace goat cheese with a dairy-free cheese alternative and use plant-based milk like almond or oat milk.

→ Can I prepare this dish in advance?

Yes, you can assemble the casserole the night before and refrigerate. Bake it fresh in the morning for best results.

→ What’s a good side dish to pair with this?

This casserole pairs well with fresh fruit, toast, or a light salad for a rounded breakfast or brunch menu.

→ Can I freeze leftovers?

Yes, let the casserole cool completely, cut it into portions, and store in an airtight container in the freezer for up to 3 months. Reheat before serving.

→ What herbs can I use for garnish?

Chopped chives, parsley, or even fresh dill work wonderfully as garnishes for added flavor and color.

Spinach Mushroom Breakfast Casserole

Vegetarian breakfast casserole with spinach, mushrooms, and goat cheese. Ideal for brunch.

Prep Time
15 Minutes
Cook Time
40 Minutes
Total Time
55 Minutes
By: Barbara

Category: Morning Favorites

Difficulty: Intermediate

Cuisine: American

Yield: 12 Servings

Dietary: Vegetarian, Gluten-Free

Ingredients

→ Vegetables

01 1 tablespoon olive oil
02 16 ounces cremini mushrooms, sliced
03 4 cups packed spinach leaves
04 2 green onions, sliced

→ Seasonings

05 3 cloves garlic, minced
06 Kosher salt and black pepper, to taste

→ Dairy

07 4 ounces goat cheese, divided
08 1/2 cup milk

→ Eggs

09 18 large eggs

→ Optional Garnish

10 Freshly chopped chives

Instructions

Step 01

Preheat oven to 350°F. Grease a 9x13-inch baking dish with nonstick cooking spray and set aside.

Step 02

In a large skillet, heat olive oil over high heat. Add the sliced mushrooms and cook until tender, about 3 minutes. Stir in the spinach and garlic. Cook for 3 minutes or until the spinach is wilted. Season with salt and black pepper, to taste.

Step 03

Pour the vegetable mixture into the bottom of the prepared pan and spread out evenly. Sprinkle sliced green onions evenly over the vegetables. Crumble half of the goat cheese over the vegetables.

Step 04

In a large bowl, whisk together the eggs and milk. Season with salt and black pepper, to taste.

Step 05

Pour the egg mixture over the veggies and cheese. Crumble the remaining goat cheese over the eggs.

Step 06

Bake for 30 to 40 minutes or until eggs are set and slightly golden around the edges. Remove from oven and let cool for 5 minutes.

Step 07

Garnish with chopped chives. Cut into squares and serve warm.

Notes

  1. Letting the casserole rest for 5 minutes after baking makes cutting slices easier.

Tools You'll Need

  • Skillet
  • 9×13-inch baking dish
  • Nonstick cooking spray
  • Mixing bowl
  • Whisk

Allergy Information

Please check ingredients for potential allergens and consult a health professional if in doubt.
  • Contains eggs
  • Contains dairy

Nutrition Facts (Per Serving)

It is important to consider this information as approximate and not to use it as definitive health advice.
  • Calories: 148
  • Total Fat: 10 g
  • Total Carbohydrate: 3 g
  • Protein: 12 g