Cut beef into 1-inch pieces. Place beef, bell pepper, mushrooms and zucchini in medium glass or plastic bowl. Stir in dressing until coated. Cover and refrigerate, stirring occasionally, at least 1 hour but no longer than 12 hours.
Heat coals or gas grill. Place potatoes in 2-quart saucepan; add enough water to cover. Heat to boiling; reduce heat to low. Simmer uncovered about 10 minutes or until almost tender; drain. Cool slightly.
Remove beef and vegetables from dressing; reserve dressing. Thread beef, marinated vegetables and potatoes alternately on each of twelve 9-inch metal skewers, leaving 1/2-inch space between each piece. Brush kabobs with dressing.
Cover and grill kabobs 4 to 5 inches from medium heat 6 to 8 minutes for medium-rare to medium doneness, turning and brushing with dressing after 3 minutes. Discard any remaining dressing.