Preheat oven to 375°F.
Heat oil in nonstick skillet over medium-high heat. Add bell peppers, onion and corn; sauté 3 to 5 minutes. Set aside.
Add black beans to large mixing bowl; mash slightly with potato masher or fork. Stir in oats, egg, mayonnaise, cilantro, chili and chipotle powders,ground cumin and salt. Stir in vegetables. Break up ground turkey and thoroughly mix in (hands work best here!). Place mixture in greased 9 x 5-inch loaf pan and bake for 1 hour.
Combine sour cream, cheddar cheese, cilantro and chili powder in a small bowl. Spread over the top of baked loaf and return pan to the oven. Continue baking an additional 15 minutes or until internal temperature reaches a minimum of 165°F. Remove from oven and let sit 5 minutes before serving.