1 teaspoon olive oil $
1 1/2 cups presliced onion $
1/2 teaspoon dried oregano
1/4 teaspoon salt $
1/8 teaspoon black pepper
1 poblano chile, seeded and chopped
1 (15-ounce) can black beans, rinsed and drained $
1 cup jarred sliced peeled mango (such as Del Monte SunFresh)
1/3 cup cubed peeled avocado $
4 (8-inch) fat-free flour tortillas $
Cooking spray $
1/2 cup (2 ounces) shredded reduced-fat sharp cheddar cheese $