Coat French bread cubes with cooking spray; place in a single layer on a baking sheet. Bake at 350 degrees for 10 minutes or until lightly browned.
Remove chicken from marinade, discarding marinade. Coat grill rack with cooking spray; place on grill over medium-hot coals (350 degrees to 400 degrees). Place chicken on rack; grill, covered, 5 minutes on each side or until done. Cut chicken into slices.
Combine chicken, bread cubes, lettuce, and next 3 ingredients in a large serving bowl. Pour remaining ¼ cup dressing over lettuce mixture, and toss well. Sprinkle with pepper, if desired.
