Combine first 3 ingredients in a small bowl, stirring well; set aside.
Coat chicken lightly with cooking spray; sprinkle with pepper and salt.
Coat grill rack with cooking spray; place on grill over medium-hot coals (350° to 400°). Place chicken on rack; grill, uncovered, 15 minutes, basting often with mustard mixture. Turn chicken, and grill 15 additional minutes or until meat thermometer inserted into thickest part of chicken registers 180°, basting often with mustard mixture.