Preheat your grill to medium-high or your oven to 400°F (200°C). Tear off four large sheets of heavy-duty aluminum foil (about 12x18 inches each).
Rub each chicken breast with olive oil, taco seasoning, salt, and pepper. Place one breast in the center of each foil sheet.
Divide the black beans, corn, and sliced bell peppers evenly among the four packets, arranging them around and on top of the chicken. Spoon about ¼ cup of salsa over each.
Fold the sides of the foil over the chicken and vegetables to seal tightly, creating a packet. Make sure no steam can escape.
Grill Method: Grill the packets for about 20–25 minutes, flipping once halfway through.
Oven Method: Bake the packets on a baking sheet for 25 minutes.
Carefully open each packet (watch for steam!) and sprinkle shredded cheese over the top. Let sit for a couple of minutes until the cheese melts. Garnish with cilantro and lime juice if desired.