Mix beef and dressing in shallow glass or plastic dish. Cover and refrigerate, stirring occasionally, at least 30 minutes but no longer than 24 hours.
Heat 1 inch water to boiling in 1 1/2-quart saucepan. Add potatoes. Boil about 15 minutes or until almost tender; drain. Cool slightly.
Heat coals or gas grill. Remove beef from marinade; reserve marinade. Thread beef, potatoes, onion, mushrooms, bell peppers and squash alternately on each of twelve 7-inch metal skewers, leaving space between each piece. Brush kabobs
generously with marinade.
Cover and grill kabobs 4 to 6 inches from medium heat 12 to 15 minutes for medium beef doneness, turning frequently and brushing with marinade. Discard any remaining marinade.