Combine all dried spices in a small bowl: chili powder, oregano, smoked paprika, cumin, salt, garlic powder, onion powder, black pepper, and cayenne pepper. Set aside. While preparing the spice blend, slice the green, red, and yellow bell peppers into ¼-inch strips, cut the red onion into ¼-inch thick wedges, slice the zucchini lengthwise then quarter each slice, and quarter the cremini mushroom caps. Arrange all cut vegetables on a large cutting board or platter for easy access during grilling.

Preheat your grill and grill topper to 350°F, allowing about 10-15 minutes for it to reach temperature. In a large bowl, toss the sliced bell peppers and red onion wedges with ½ tablespoon of avocado oil until evenly coated.

Once the grill reaches temperature, carefully spread the oiled peppers and onions in an even layer on the grill topper. Grill for about 15 minutes, stirring halfway through.

While the peppers and onions finish cooking, toss the quartered zucchini with ½ tablespoon of avocado oil in a separate bowl. After 2-3 minutes, add the mushroom quarters that have been tossed with the remaining ½ tablespoon of avocado oil.

Once all vegetables are on the grill, sprinkle about 2 teaspoons of the spice blend from Step 1 evenly over everything and gently toss to coat. Continue grilling for another 2-3 minutes.

While the vegetables finish cooking, warm your corn tortillas on the grill or in a dry skillet over medium heat for about 30 seconds per side. Transfer the finished grilled vegetables to a serving platter.