1. Combine all ingredients except lamb in a large bowl; stir with a wire whisk. Add lamb, stirring gently to combine. Cover and marinate in the refrigerator at least 8 hours, up to 24 hours.
2. Remove lamb from marinade, reserving marinade. Set meat aside.
3. Place marinade in a saucepan, bring to a boil, reduce heat and simmer 5 minutes. Remove from heat and set aside.
4. Place lamb on metal skewers; grill over medium coals or broil 4 to 6 inches from heat 8 to 10 minutes on each side or to desired degree of doneness, basting frequently with marinade.