MIX all ingredients except chicken until well blended.
PLACE chicken in shallow glass dish or resealable plastic bag. Add 1/3 cup of the mustard mixture, turning to coat. Cover; refrigerate at least 1 hour. Remove chicken from marinade; discard marinade.
PREHEAT greased grill to medium-high heat. Grill chicken 6 to 8 minutes on each side or until cooked through. Heat remaining mustard mixture; serve with chicken.