Fold a 36x18-inch piece of heavy foil in half and make an 18-inch square.
Place red or green pepper, onion, and garlic on the foil. Drizzle with olive oil and balsamic vinegar. Sprinkle with salt and pepper. Toss to mix.
Bring up two opposite edges of foil; seal with a double fold. Fold remaining ends to enclose mixture, leaving space for steam to build.
Trim fat from rib eye steak. Rub your favorite seasoning blend over steak. Grill the packet and steak on the rack of an uncovered grill directly over medium coals. Grill the packet 20 minutes or until the vegetables are tender, turning once. For the steak, allow 8 to 12 minutes for medium rare (12 to 15 minutes for medium), turning once halfway through.
Cut steak into serving-size pieces and serve with pepper mixture.