Step 1. Stack two 20-inch sheets of foil (the double layers will help protect the ingredients on the bottom from burning). Coat the center of the top layer with cooking spray.
Step 2. Layer your ingredients on the foil. Center everything: it’s easier to wrap the food and makes the packet look neat.
Step 3. Bring the short ends of the foil together, leaving enough room in the packet for steam to gather and cook the food. Fold the foil over and pinch to seal. Pinch seams together along the sides. Make sure all the seams are tightly sealed to keep steam from escaping.
Step 4. Place the packets on a gas grill over medium heat or on a charcoal grill 4 to 6 inches from medium coals. Cover the grill and cook just until the packet contents are done. Handle the hot packets with a large spatula or oven mitts. Carefully open both ends of the packet and allow the hot steam to escape.