Serves 4
If desired, pound chicken to an even thickness of 1/2 inch (1 1/2 cm).
Mix mustard, oil, honey, Worcestershire sauce, vinegar, orange juice, lemon juice, parsley, and pepper in a gallon-size ziplock bag. Add the chicken and toss until evenly coated. Seal the bag and allow the chicken to marinate for 10–15 minutes.
Preheat grill or grill pan to medium-high heat. Spray the grill or grill pan with cooking spray. Place the chicken on the grill and cook for 3 minutes per side.
Transfer chicken to a serving platter and serve warm or at room temperature.
Tip: If your chicken is thicker, cover the grill or grill pan to ensure that the chicken cooks through.