While grill heats, prepare Caesar Dressing. Reserve 1/3 cup dressing in a separate bowl; set aside.
Place chicken on grill rack coated with cooking spray over medium-high heat. Grill 2 to 3 minutes on each side or until done, basting frequently with remaining dressing.
Remove from grill. Cool slightly; slice.
Combine chicken, reserved 1/3 cup dressing, lettuce, and tomato in a large bowl; toss gently to coat. Divide salad evenly among each of 4 bowls.