Place corn, pepper and onion in hot grill pan. Add enough asparagus spears to fit in single layer on bottom of pan. Brush vegetables in pan evenly with half the dressing. Grill 8 to 10 min. or until corn and asparagus are softened and lightly browned, turning occasionally. Remove corn and cooked asparagus from pan. Add remaining asparagus to peppers and onions in pan; brush asparagus with remaining dressing. Cook 8 to 10 min. or until all vegetables are softened, turning occasionally. Remove vegetables from pan; cool slightly.