Portobello Fajitas

By Updated on

Amazing vegetarian portobello fajitas are a delicious plant-based spin on the original. Meaty portobello mushrooms, crisp bell peppers, and sweet red onions are all served in warm tortillas. Top everything off with creamy avocados and a squeeze of lime juice for a flavor-packed meal!

328 CAL 44g CARBS 16g FAT 8g PROTEIN 7
Leave a Comment

While fajitas are traditionally prepared with grilled meat and veggies, we often find ourselves making Portobello Fajitas for a plant-forward approach. This recipe is proof that vegetarian alternatives can be just as savory and satisfying!

Portobello mushrooms act as a meat substitute in this recipe, offering a hearty, earthy flavor and a tender, meaty texture that even non-vegetarians will love. The bell peppers and red onions add a touch of sweetness and color, while the fajita seasoning brings heat and depth.

Once everything is pan-fried, we love serving our fajitas with a side of warm flour or corn tortillas, avocado slices, lime wedges, and a sprinkle of chopped cilantro. But you can pile on any fajita toppings you like.

For more vegetarian fajitas, check out our roasted vegetable fajitas, eggplant fajitas, and tofu fajitas.

Why You’ll Love Portobello Fajitas

These portobello mushroom fajitas are one of our favorite meals during the week! Here’s why:

  • Made in one pan: Everything comes together in just one skillet, making this recipe great for quick weeknight dinners.
  • Great for vegetarians: This is a great option to make for meat-free Mondays or plant-based friends and family members.
  • Rich in flavor: The homemade fajita seasoning perfectly infuses the veggies with a blend of smoky, spicy, and savory notes.

Mushroom fajitas with portobello mushrooms, bell peppers, red onions, cilantro, lime, avocado, and sour cream in warm tortillas.

Ingredients & Substitutions

Here are the ingredients you’ll need for portobello fajitas:

  • Portobellos: These large mushrooms have a meaty texture and robust flavor, making them an excellent meat substitute. Button or shiitake mushrooms will also work.
  • Bell peppers: Add a sweet, slightly tangy flavor and a crunch. Feel free to use any color you prefer like yellow bell peppers or red bell peppers.
  • Red onion: Provides a sweet and savory flavor once cooked. Yellow or white onions are also good options.
  • Olive oil: To sauté the vegetables and add depth of flavor. You can also use other vegetable oils like canola or avocado.
  • Seasonings: We use a smoky and spicy mixture of chili flakes, cayenne pepper, garlic powder, cumin, smoked paprika, salt, and pepper. If you don't have these spices on hand, use a pre-made fajita blend or your own homemade taco seasoning. You can also add spices like chili powder and chipotle powder.

How To Make Portobello Fajitas

1. Prep The Veggies & Seasoning

Begin by slicing the bell peppers, red onion, and portobello mushrooms into strips. Since the vegetables will shrink as they cook, it’s best to slice them thicker than you’d like them to turn out. Meanwhile, toss all your fajita seasoning spices together and set the bowl aside.

2. Cook The Veggies

Make sure to use a large skillet to fit all of the veggies without overcrowding it too much. Cook the bell peppers in some olive oil followed by the onions. Once those are softened, add the sliced mushrooms and cook them until they're tender.

Add the fajita seasoning blend to the softened vegetables and mushrooms, giving everything a good stir to release the flavors of the spices.

Ingredient Spotlight: Portobello Mushrooms

Portobello mushrooms are a staple ingredient for vegetarian cooking due to their versatility and rich flavor. Here’s why we love them:

  • Flavor and texture: Portobello mushrooms have a robust, earthy flavor that many describe as 'meaty.' This makes them a satisfying substitute for meat in many dishes.
  • Nutrition: Portobellos are low in calories, yet high in essential nutrients like potassium, selenium, and B vitamins.
  • Culinary uses: Due to their large size and hearty texture, portobello mushrooms can be used in a variety of dishes. They can be grilled, roasted, or sautéed and are commonly used in sandwiches, stews, and fajitas.

When shopping, look for portobellos with smooth, unblemished caps. They should be firm to the touch, not slimy or soft. Store them in a paper bag in the refrigerator to keep them fresh.

What To Serve With Portobello Fajitas

Serve your portobello fajitas in warm tortillas and top them with flavor-packed garnishes and sides like these:

Vegetarian fajitas made with sliced portobello mushrooms, peppers, onions, avocado, and sour cream in a tortilla.

Storage and reheating

Portobello fajitas make for great leftovers and meal prep. Just follow these simple storage instructions:

  • Fridge: Once cooled, store the fajita mixture in an airtight container for up to 4 days.
  • Freezer: You can freeze the fajita mixture in a freezer-safe container for up to 3 months.
  • Reheating: Reheat the fajitas in a skillet over medium until warmed through. We like to add a bit of oil to the pan to ensure everything becomes crispy again.
  • Prep ahead: The vegetables and fajita seasoning can be prepared ahead of time and stored in the fridge. When you’re ready to cook, simply sauté the vegetables and add the seasoning.

Easy Variations To Change The Flavor

We’re always on the hunt for more ways to add flavor to our recipes so we can continue to reuse them without getting bored! Here are some easy variations so you can keep making this recipe over and over again:

  • Add protein: If you're not vegetarian, mix in some cooked chicken or beef to the fajitas.
  • Cheese: Add a sprinkle of shredded cheddar cheese, queso fresco, or Cotija on top.
  • Beans: Add cooked black beans or pinto beans to the veggie mix.
  • Grilled: For a smoky, charred flavor, roast the vegetables on a grill instead of sautéing them.

Frequently Asked Questions

Here are the most common questions about these mushroom fajitas.

At baseline, these fajitas are already vegan-friendly. Just double-check that the flour tortillas you use don’t contain dairy or lard. Also, be mindful of extra toppings you use like cheese or sour cream.

Of course! Some other options you can choose from include button mushrooms, cremini mushrooms, oyster mushrooms, or shiitake mushrooms.

You can serve the fajita mix over brown rice, quinoa, or in lettuce wraps for a gluten-free and lower-carb option.

Vegan mushroom fajitas with portobellos, red onions, sliced peppers, avocado, and lime in three tortillas.
The Recipe
Portobello mushroom fajitas with peppers, onions, mushrooms, guacamole, and sour cream in a warm corn tortilla.

Portobello Fajitas

328 CAL 44g CARBS 16g FAT 8g PROTEIN 7
Leave a comment
  • Print
  • Download
  • Send to your inbox


  • 1 lb portobello mushrooms, sliced
  • 1 red bell pepper
  • 1 yellow bell pepper
  • 1 green bell pepper
  • 2 red onion
  • 2 tbsp olive oil
  • 1/2 tsp chili powder (seasoning)
  • 1/8 tsp cayenne pepper (seasoning)
  • 1 tsp garlic powder (seasoning)
  • 1 tsp ground cumin (seasoning)
  • 1 tsp smoked paprika (seasoning)
  • 1/2 tsp salt (seasoning)
  • 1/2 tsp ground black pepper (seasoning)
  • 1 avocado
  • 1 lime
  • 1/2 cup cilantro, chopped
  • 8 corn tortillas

Like this Recipe? Try our Meal Plans!

Slender Kitchen Meal Plans
  • Weekly Meal Plans
  • Easy Shopping List
  • Healthy, Low Carb, & Vegetarian
  • Nutritional Information


(Hide Media)

Switch to prevent your screen from going dark.


Prepare your veggies. Chop bell peppers and red onion into strips, and portobellos into slices. Then, mix all the spices for the fajita seasoning and set them aside.

Sliced bell peppers and red onions in a bowl.

Heat a large skillet, add olive oil, and then chopped bell peppers. Stir until pepper begins to soften, then add red onion and stir until it is translucent. Fold in sliced mushrooms and cook until soft and tender.

Cooked bell peppers and onions in a skillet.

Add the fajita seasoning and stir until well combined, for about 1 minute.

Fajita seasoning being added to a skillet with peppers, onion, and portobellos.

Serve with warmed tortillas with fresh avocado, lime juice, and chopped cilantro.

Mushroom fajitas with guacamole and sour cream on a flour tortilla.


This equipment section may contain affiliate links to products we recommend.
Nutritional Facts
Serving Size: 2 fajitas
Amount Per Serving
Calories 328
Calories from Fat 147
% Daily Value *
Total Fat 16g
Saturated Fat 2g
Monounsaturated Fat 0g
Polyunsaturated Fat 0g
Cholesterol 0mg
Sodium 344mg
Total Carbohydrate 44g
Dietary Fiber 11g
Sugars 8g
Protein 8g

* Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.

The Nutritional Values provided are estimates only and may vary based on the preparation method.


Optional: Drizzle with sour cream, Mexican crema, or vegan sour cream.

user image
About the author Meet Kristen McCaffrey
Hi, I’m the cookbook author, recipe developer, and food enthusiast behind Slender Kitchen. I am obsessed with making healthy food that is easy to prepare and absolutely delicious. Meal planning is my secret weapon and I hope I can make meal time easier for you with our tried and tested recipes and foolproof meal plans. Learn More
On Portobello Fajitas
user image
Instagram Icon
Did you make this?

Snap a picture and show us what you made on Instagram or Facebook. Tag us using @SlenderKitchen or #slenderkitchen.