Trim fat from lamb. Combine soy sauce and next 6 ingredients in a heavy-duty zip-top plastic bag. Add lamb; seal bag, and shake until lamb is well coated. Marinate in refrigerator 8 hours, turning bag occasionally.
Remove lamb from marinade, reserving marinade. Place marinade in a saucepan, and bring to a boil. Remove from heat. Place lamb on grill rack coated with cooking spray; grill, covered, 15 minutes on each side or until meat thermometer registers 145° (medium-rare) or desired degree of doneness, turning and basting occasionally with reserved marinade.