1Heat gas or charcoal grill. Brush chicken with 1 tablespoon of the dressing. Carefully brush oil on grill rack. Place chicken, zucchini and onion on grill over medium heat. Cover grill; cook 8 to 10 minutes, turning once, until chicken is no longer pink in center and vegetables are tender. Add tomato halves to grill for last 4 minutes of cooking.
2Remove chicken and vegetables from grill to cutting board. Cut chicken crosswise into thin slices; coarsely chop vegetables.
3In large bowl, toss chicken, vegetables and remaining 6 tablespoons dressing. Add arugula and cheese; toss gently. Serve immediately.