Combine first 4 ingredients and set aside. Pierce each breast a couple times on both sides with a fork. Brush some of the soy sauce mixture over chicken, coating both sides and reserving some for basting. Cover and refrigerate for at least 30 minutes.
Grill or broil chicken breasts over medium heat 8-10 minutes or until no longer pink. Frequently baste and turn chicken during cooking and discard any remaining marinade.
