1. In a shallow glass baking dish, or plastic bag, pour 1/2 cup of the salad dressing over the chicken breasts. Cover or close the bag and marinate in the refrigerator for at least 1 hour, or overnight, turning once in awhile.
2. Just before grilling preheat gas grill on High-Heat for about 10 minutes. Reduce heat to Medium-Heat.
3. Remove the chicken from the marinade and discard the marinade.
4. Place chicken breasts on hot grill and grill for about 8 to 9 minutes per side, brushing frequently with remaining 1/4 cup of salad dressing. Chicken is done when no longer pink in the center and the juices run clear.