Make the fajita seasoning by combining the chili powder, cumin, smoked paprika, salt, garlic powder, onion powder, and cayenne pepper in a small bwl. Mix together well. This will make 2 Tablespoons of the seasoning.
Preheat oven to 350° Fahrenheit.
Slice the portobello mushrooms into ½-inch strips.
Cut the green, red, and yellow bell peppers into thin strips.
Slice ½ of the onion into thin strips.
Scatter all the vegetables on a sheet pan. Drizzle with olive oil and all of the fajita seasoning. Make sure all of the vegetables are evenly coated.
Bake in the oven for 15 minutes. Remove from oven and give the vegetables a good mix to make sure everything is cooking evenly. Then bake for another 15 minutes.
Warm the wraps in between damp paper towels in the microwave for about 15 seconds. This will help to make them more pliable.
Place the portobello/veggie fajita mix into the warmed wraps. Top with shredded lettuce, guacamole, fresh salsa, and garnish with cilantro and lime wedges.