Heat gas or charcoal grill. Cook pasta as directed on package. Drain; rinse with cold water to cool. Drain well.
Meanwhile, brush chicken with 1 tablespoon of the dressing (if desired, sprinkle chicken with salt and pepper).
When grill is heated, place chicken, zucchini, bell pepper (skin side down) and eggplant on gas grill over medium heat or on charcoal grill over medium coals; cover grill. Cook 10 to 13 minutes, turning once, until juice of chicken is clear when center of thickest part is cut (170°F) and vegetables are tender.
Cut chicken and vegetables into bite-size pieces; place in large bowl. Gently stir in cooked pasta and lettuce. Pour remaining dressing over salad; toss gently to coat.