Sheet Pan Portabello Mushroom Fajitas

These vegetarian portobello mushroom fajitas are bursting with flavor! The mushrooms are cooked on a sheet pan with the peppers and onions to speed things up so they’re a weeknight-friendly crowd-pleaser.

  • Author: Leanne Ray, MS, RDN
  • Prep Time: 20 minutes
  • Cook Time: 20 minutes
  • Total Time: 40 minutes
  • Yield: 4 servings 1x
  • Category: Mains
  • Method: Oven
  • Cuisine: Mexican
  • Diet: Vegetarian


  • 1/4 cup soy sauce
  • 2 Tbsp red wine vinegar
  • 3 Tbsp neutral oil (like canola or grapeseed) – divided
  • 1/2 tsp granulated garlic
  • 1/2 tsp ground cumin
  • 1/8 tsp crushed red pepper flakes
  • 2 portabello mushroom caps
  • 1 red bell pepper
  • 1 red onion
  • 8, 6 inch flour tortillas
  • for serving: diced tomatoes, diced avocado, fire-roasted corn, shredded cheese, sour cream, cilantro, lime wedges 


  1. Preheat oven to 375 degrees. 
  2. Prepare a sheet pan with nonstick cooking spray. 
  3. Make the marinade by adding soy sauce, vinegar, 2 tablespoons of the oil and spices to a small jar. Cover tightly and shake until thoroughly combined. 
  4. Prep portabello mushrooms: remove stems, clean out the gills with a spoon, and wipe the top of the cap clean with a damp towel. Cut into 1/2″ slices and add to a medium bowl, then pour the marinade over the top and toss to coat. Let sit at least 10 minutes. 
  5. Meanwhile, slice bell pepper and red onion and add to sheet pan. Toss with the remaining tablespoon of oil and season with salt and pepper. Once mushrooms are done marinating, add to sheet pan. Transfer to oven and cook for 20 minutes. 
  6. To assemble, add mushrooms, bell peppers and onions to a tortilla and add your favorite toppings.



  • The equipment section above includes affiliate links to things I use often in my kitchen and recommend.
  • Nutrition information was calculated for fajitas without toppings since this may vary.
  • I love keeping frozen fire-roasted corn on hand. It’s available at many grocery stores now!


Keywords: vegan fajitas, portabello mushrooms, vegan mexican recipes, sheet pan meals