Pour ½ cup dressing over chicken in large nonaluminum baking dish or plastic bag. Cover or close bag and marinate in refrigerator, turning occasionally, 30 minutes or up to 3 hours. Remove chicken and discard marinade. Grill or broil, turning once, brushing with additional ¼ cup dressing. Thinly slice chicken.
Arrange salad greens, strawberries, avocado and tomatoes on platter. Top with chicken and sprinkle with walnuts. Drizzle, if desired, with additional dressing.