Brush chicken and onion with 1/2 cup salad dressing; set aside. Combine 1/4 cup salad dressing and cabbage; mix well; set aside. Grill chicken over hot coals 5 to 7 minutes on each side or until no longer pink in center. Sprinkle chicken evenly with Swiss cheese during the last minute of grilling. Grill onion 4 to 5 minutes on each side, or until browned and tender. Grill rolls until toasted. Spread toasted sides of rolls with remaining 1/2 cup salad dressing. Place chicken on roll bottoms. Top with onion, cabbage mixture and roll tops. Serve immediately.