This mushroom frittata is a delicious and easy vegetarian egg breakfast that makes my busy mornings feel a little more luxurious! Fluffy eggs, sautéed mushrooms, wilted spinach, and melty Gruyère come together to create a cozy, satisfying dish for breakfast or brunch. I love making this spinach mushroom frittata when I want something comforting yet simple and veggie-forward, especially when feeding a crowd.
Spinach and Mushroom Frittata
After years of making my go-to ham and cheese frittata, this spinach and mushroom frittata has been a refreshing change of pace. It’s now my favorite vegetarian frittata to bring to potluck brunches. With hearty mushrooms and savory Gruyère, it never feels like anything is missing, even without meat.
This recipe is flexible and forgiving, which is why I make it so often. I cook the vegetables first to remove excess moisture, a simple step that makes all the difference for creamy, well-set eggs. Once you’ve mastered that, this mushroom frittata becomes an easy staple you can adapt again and again.
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How to Prevent Grainy Eggs in a Frittata
After sautéing the mushrooms and spinach, let the mixture cool on a plate for 2-3 minutes before adding it back to the eggs. Hot vegetables can partially cook the eggs on contact, which causes a grainy texture. This short pause helps the eggs stay smooth and allows the frittata to bake evenly with a soft, creamy center every time.
Mushroom Frittata Recipe
Equipment
- Cast Iron Skillet
Ingredients
- 12 large eggs (1 carton)
- ½ cup milk
- 1 teaspoon kosher salt (divided)
- ¼ teaspoon ground black pepper
- 2 tablespoons olive oil (divided)
- 1 shallot (finely chopped)
- 2 cloves garlic (minced)
- 2 sprigs fresh thyme
- 8 ounces cremini mushrooms (sliced*)
- 2 cups fresh spinach (**)
- 1 cup shredded Gruyère cheese (***)
- grated Parmesan cheese (optional, for topping)
Instructions
- Preheat oven to 425°F. Whisk the eggs, milk, ½ teaspoon salt, and pepper in a large bowl.12 large eggs, ½ cup milk, 1 teaspoon kosher salt, ¼ teaspoon ground black pepper
- Heat 1 tablespoon of oil in a large oven-safe skillet over medium heat. Add in the shallot and ¼ teaspoon salt, and sauté until softened, about 3-4 minutes.2 tablespoons olive oil, 1 shallot
- Stir in the garlic and thyme leaves and cook until fragrant, about 1 minute.2 cloves garlic, 2 sprigs fresh thyme
- Add in the mushrooms and ¼ teaspoon salt, and cook until softened and the excess liquid has been evaporated, about 3-5 minutes.8 ounces cremini mushrooms
- Stir in the spinach and cook until wilted, about 3 minutes.2 cups fresh spinach
- Transfer the mushroom mixture to a plate or bowl.
- Heat another tablespoon of oil in the skillet and swirl it around until it covers the bottom of the pan.
- Pour the egg mixture into the pan. Add the mushroom and spinach mixture in an even layer over the eggs, and sprinkle Gruyère cheese over top.1 cup shredded Gruyère cheese
- Transfer the skillet to the oven, and bake for 15 minutes, until the eggs have just set. Top with additional fresh thyme and grated Parmesan cheese, if desired.grated Parmesan cheese
Notes
- I recommend using a cast-iron skillet for the most even cooking.
- Whisk the eggs vigorously to incorporate air, which helps make the frittata lighter.
- Always cook your veggies in the pan before adding your eggs. Leave everything slightly underdone; it will finish cooking in the oven.
- Take care not to burn the shallot or garlic; this could lead to a bitter-tasting frittata.
- Mix in caramelized onions, bacon bits, sautéed leeks, asparagus, zucchini, broccoli, or any other veggies you might have in your fridge.
- Shred a block of cheese to avoid the added starch in pre-shredded cheese. Finely shredded also melts better without getting a gritty texture.
- Don’t stir the eggs once they’re in the pan; let them set gently for a clean frittata texture.
- You can gently lift the edges of the frittata while it’s baking so uncooked egg can flow underneath; this helps the center set evenly and stay creamy.
- If the top browns too quickly, cover loosely with foil for the remainder of the baking time.
- A frittata is finished baking when the edges are lightly browned and firm, but the center is still slightly jiggly. You want the center to remain creamy.
- Let the frittata rest for 5 minutes after baking. This helps it set further and makes slicing easier.
- To flip your frittata, place a plate face down on top of your skillet, then flip so that the frittata falls nicely onto the plate.
- Serve warm, at room temperature, or even cold for meal prep-friendly breakfasts.
- To reheat without drying out, cover with foil and warm in a 350°F oven for 10-15 minutes.
- Nutritional information does not include optional ingredients.
Note: Water, salt, pepper, oil, and broth are not counted as ingredients on this site.
How to Make a Mushroom Frittata Step by Step
Prep: Preheat your oven to 425°F. Finely chop the shallot, mince the garlic, slice the mushrooms, and shred the cheese. Vigorously whisk 12 large eggs, ½ cup of milk, ½ teaspoon of kosher salt, and ¼ teaspoon of ground black pepper in a large bowl.
Sauté the Veggies: Heat 1 tablespoon of oil in a large oven-safe skillet set over medium heat. Add in 1 finely chopped shallot and ¼ teaspoon of kosher salt, and sauté until softened, about 3-4 minutes. Stir in 2 minced cloves of garlic and 2 sprigs of fresh thyme and cook until fragrant (careful not to burn them!), about 1 minute. Add in 8 ounces of sliced cremini mushrooms and ¼ teaspoon of kosher salt, and cook until softened and the excess liquid has evaporated, about 3-5 minutes. Stir in 2 cups of fresh spinach, and cook until wilted, about 3 minutes. Transfer the mushroom mixture to a plate or bowl.
Assemble and Bake: Heat another tablespoon of oil in the skillet and swirl it around until it covers the bottom of the pan. Pour the egg mixture into the pan. Add the mushroom and spinach mixture in an even layer over the eggs, and sprinkle 1 cup of shredded gruyère cheese over top. Don’t stir the eggs once they hit the pan, or the frittata won’t cook correctly. Transfer the skillet to the preheated oven, and bake for 15 minutes, or until the eggs have just set. You can gently lift the edges of the frittata early in the bake to allow uncooked egg from the center to flow underneath, and you can top with aluminum foil if it’s browning too fast. You’ll know it’s done when the edges are browned and firm, but the center is still slightly jiggly. Top with additional fresh thyme and grated Parmesan cheese, if desired. Let it set for 5 minutes before slicing and serving.
How to Store, Freeze, and Reheat
Store leftover mushroom frittata in an airtight container in the refrigerator for up to 3 days. To freeze, tightly wrap it in 2 layers of plastic wrap and 1 layer of aluminum foil, then store for up to 2 months. Reheat in a lightly greased oven-safe dish at 350°F covered with foil for 10 minutes. Remove the foil in the last few minutes to crisp the top. If frozen, defrost before reheating for best results.
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