Place chicken in a heavy-duty, zip-top plastic bag; pour ¼ cup dressing over chicken. Seal bag, and shake until chicken is well coated. Marinate in refrigerator 1 hour, turning bag once.
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.
Note: Yield: 6 Servings, Serving Size: 2 cups, Degree of Difficulty: Medium