- Combine mustard, maple syrup, and vinegar 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 (350-400 degrees).
- 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 degrees, basting often with mustard mixture.