1. Prep charcoal grill with medium-hot coals or heat gas grill to medium-high heat.
2. In a large bowl, stir together olive oil, lime zest, lime juice, 1 teaspoon of the chili powder, 1/2 teaspoon of the salt and 1/4 teaspoon of the pepper. Add corn, peppers, onion and garlic; stir to coat.
3. Using 12-inch-wide heavy-duty aluminum foil, cut 4 pieces 32 inches long; fold each piece in half to make a 16 x 12-inch rectangle. Generously coat foil pieces with nonstick cooking spray.
4. Evenly divide mixture on one half of each foil piece. Sprinkle tilapia with remaining 1/2 teaspoon chili powder, 1/2 teaspoon salt and 1/4 teaspoon pepper. Place seasoned fillets on top of vegetables in foil.Create a packet:
5. Fold second half of foil over fish and vegetables. Tightly seal sides and front edges, leaving space for steam to build. Place foil packets on grill rack; grill 20 minutes. Carefully open packets; transfer contents to 4 serving plates. Sprinkle with cilantro.