In a large bowl, combine beef, salad dressing, bread crumbs, onion, salt and pepper. Shape into 6 patties. Grill over medium-hot coals 5 to 6 minutes until no longer pink in center (160 degreesF). Place on sesame seed buns with lettuce, tomato and red onion slices, if desired. Serve with a generous amount of additional salad dressing.