Vegetable Fajitas

Name: Vegetable Fajitas
Ingredients: 2 tablespoons olive oil; 1 large onion, halved and sliced; 1 red bell pepper, cut into strips; 1 yellow bell pepper, cut into strips; 1 green bell pepper, cut into strips; 8 ounces mushrooms, stems removed, sliced; 1 tablespoon chili powder; 2 cloves garlic, minced; 1/4 teaspoon salt; teaspoon ground black pepper; 4 whole wheat tortillas (8 diameter); 1 small ripe avocado, sliced; 1/2 cup grape tomatoes, sliced (about 12 tomatoes); 1/4 cup chopped fresh cilantro; sprigs for garnish (optional)