Preheat the oven to 425 degrees and line 2 baking sheets with parchment paper.
Use your hands to shred the mushrooms and add them to a baking sheet with 1 tablespoon of oil & 1 tablespoon of taco seasoning. Toss to coat and spread in an even layer.
Add the onion, bell pepper and remaining oil & taco seasoning to the other baking sheet. Toss to coat and spread in an even layer. Place both baking sheets in the oven for 15 minutes. Toss and place back in the oven for 5 minutes (see notes).
Meanwhile, combine the mayo, salsa verde & lime juice in a bowl.
Remove the veggies from the oven and replace the parchment paper on one of the baking sheets. Heat the tortillas (see notes) and working one at a time, brush one side with oil, flip it over and spread out 1 tablespoon of sauce. Add some veggies and fold to close. Place on the prepared baking sheet and repeat with the remaining ingredients. Place in the oven for 10 minutes, flip and cook for another 5-7 minutes. Remove from the oven.
Serve hot with your favorite toppings.
Video
Notes
The baking time for the veggies will depend on how thin you make them and how crispy you like them. Toss them after 15 minutes and then decide whether you want to put them back in.
I like to heat the tortillas by wrapping them in a damp paper towel and microwaving them for 30-60 seconds.