Preheat oven to 450 F and move one rack to the top slot in the oven.
In a large bowl, whisk together all the marinade ingredients.
Toss the mushrooms in the marinade until evenly coated. Let sit for 30 minutes. Toss peppers and onions with 1 tablespoon of olive oil and 1/4 teaspoon of salt.
Spread marinated mushrooms, onions, and peppers across an oiled baking sheet with a rim and bake for 20 minutes.
Move pan to top rack and broil for 2 additional minutes to add some char to the veggies.
Serve with warm tortillas, salsa, guacamole or avocado, and fresh cilantro.