Spinach and Mushroom Frittata

Making a spinach and mushroom frittata is as easy as making an omelet. The frittata is made for serving many people at once. Serve this frittata alone or with a side of Lemon Dill sauce on the side.

Spinach Mushroom frittata is a great way to make a healthy brunch.
Spinach Mushroom frittata is a great way to make a healthy brunch.

Traditionally an Italian dish, Frittatas are a great way to use those end-of-week leftovers that end up in the fridge.

Even though this is called a spinach and mushroom frittata, this frittata is similar to a French Onion frittata but instead is made with Portobello mushroom, spinach, onion and cheddar, but you can add whichever toppings of your choosing. Frittatas are a very versatile dish that you can add almost anything to. Add your favorite meats, cheeses or veggies to the dish, and then pour the eggs on top.


  • Eggs: The base of any frittata is eggs! Whisk well before pouring into your cooked toppings.
  • Spinach: Use a couple handfuls of freshly washed spinach.
  • Onions: You’ll be caramelizing these onions so you will want to pick an onion with a lot of natural sugar. My favorite is a sweet yellow onion.
  • Mushrooms: Baby Bellas or whole Portobellos will work. Just cut into bite size pieces.
  • Cream: Adding cream to your eggs with give your frittata creaminess as well as help it cook evenly. You can replace the cream with milk if you’d like, but the half and half in this recipes is necessary if you ask me!

How to Make a Frittata

First, you will want to prepare your ingredients before adding them together and preheat your oven to 350 degrees. Crack the eggs and add the half and half to the cracked eggs. Whisk together until smooth and set aside. Chop your onions and mushrooms if they are not already chopped.

Add the olive oil to a frying pan and heat over medium heat. Allow the oil to get hot and add the onion. Cook for about 10 minutes or until the onions have started to brown. Once slightly brown, add the butter and the mushrooms. Once the mushrooms have slightly browned, add the spinach and toss well. When the spinach is wilted, add all the contents to your frittata dish and arrange as desired.

Once all your toppings for your frittata are cooked and in your dish, add your whisked eggs to the top of the dish.

Put the dish in your preheated oven for 20 minutes. If you want to check to see if your frittata is done cooking, it should be slightly soft in the middle by not soupy.

Once the frittata is done cooking, take it out of the oven and allow it to rest for 15 minutes. It will continue cooking once it is out of the oven.

After resting, serve with a sauce or plain.

What is a Frittata?

Often, a frittata is referred to as a “crustless quiche”. It’s what you would expect a baked omelet or scramble to taste like. The benefit of making a frittata instead of a scramble is you can make it into any shape you’d like, and you can make a bigger portion to serve a larger audience.

Best Toppings for a Frittata

Almost any topping is acceptable for a frittata. When choosing what you would like to put into your frittata, think about what is easy to cook down and what has minimal water in it. Zucchini, for example, may be more difficult to put into your frittata because of its high water content. If you do choose something like this, make sure to extract as much water from it as possible by sweating it first and then sauteeing it fully.

Arrange your veggies in the quiche pan before pouring in your eggs
Arrange your veggies in the quiche pan before pouring in your eggs

For this frittata, I sliced some onions and then caramelized them. After they were caramelized I added in a diced portabella mushroom and then wilted some spinach. After one veggie was cooked, I would transfer it to my quiche dish and continue cooking down the veggies.

Pour the eggs over your caramelized onions and other veggies.
Pour the eggs over your caramelized onions and other veggies.

People also ask about common frittata mistakes

How much is too much cream or milk?

Adding too much dairy to your frittata is almost as bad as not adding enough. If too much dairy is added, it’s possible the dairy could curdle when it’s cooked in the oven due to the high heat. When cooking with eggs and dairy, follow this ratio: 12 eggs to 1/2 cup of full-fat dairy.

What if I don’t add any milk or cream to my frittata?

Forgetting to add cream or milk to the mixture is a cardinal sin when making frittatas. A full-fat dairy will help give the frittata its signature fluffy texture. If dairy is not added, the egg mixture will become too dense and will not cook correctly.

Over baking your Frittata

Worse than underbaking the frittata is overbaking. It’s best to take the frittata out of the oven after 20 minutes and cut a small slit in the middle of it to check for doneness. If the eggs are still liquid in the middle, bake for another 5 to 7 minutes. If the frittata is semi-solid when you cut into it, let it sit for a couple of minutes and let it harden up on its own. The residual heat should continue to cook the eggs.

Not Cooking the Veggies before Baking

While the veggies will cook a bit in the oven when the frittata is baking, it’s best to cook the veggies to their desired doneness before pouring the eggs on top.

Spinach and Caramelized Onion Fritatta

0.0 from 0 votes
Recipe by Sarah
Course: BreakfastCuisine: Italian, AmericanDifficulty: Easy


Prep time


Cooking time






  • Prep. Slice the onions and wash your spinach. Dice your mushroom and set it aside. Take a quiche or frittata pan and spray it with nonstick spray. Set your oven to 350 degrees.
  • Caramelize the onion. Add your oil to a large nonstick pan over medium heat. Take your onion slices and add them to the oil. After about five minutes, add the butter. After the onions have achieved the desired caramelization, add the diced mushroom. Add the cooked veggies to your frittata pan.
  • Wilt the spinach. With the leftover butter in the pan, add in your spianch and let it wilt down completely, about 7 minutes. Transfer to the frittata pan. Arrange the veggies in the pan as you would like, as you will be unable to when the egg is poured over them.
  • Eggs. Beat your eggs and cream together. Then add the cheese. Pour the mixture over the spinach, mushroom and onion.
  • Bake. Bake your frittata for 20 minutes and finish it by broiling for 3 minutes, it will give it a golden-brown crust on top. If the frittata is still running in the center, bake for another couple of minutes.
  • Let rest. Let the frittata rest for at least five minutes before cutting into it. This will help any still-soft eggs thicken a bit before serving.

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