Preheat the oven to 375 degrees F. Set out a 13x9-inch baking dish.
In a medium mixing bowl, combine black beans, corn, green chiles, tomato, bell pepper and cilantro. Set aside.
Spray the large casserole dish with nonstick cooking spray. Arrange the chicken breasts in the dish and sprinkle both sides with salt and pepper. Sprinkle with taco seasoning and rub into both sides. Spread the black bean mixture evenly over the top, and then the cheese.
Bake, uncovered, for 35-40 minutes, or until the chicken is fully cooked (165 degrees F) and the mixture is bubbly.
Remove from the oven and let sit for 5 minutes before serving. Additional minced cilantro can be used for garnish.
Make ahead - you can prep the chicken with the seasoning about a day in advance, and prep the topping as well, storing it separately.Storage - Store leftover southwest chicken in an airtight container for up to 3-4 days in the fridge.Reheating - Reheat in the individual portions in the microwave, or larger portions in the oven at 350 degrees, covered with foil.