Place packs on grill over medium heat. Cover grill; cook 12 minutes. Rotate packs 1/2 turn; cook 10 to 12 minutes longer or until potatoes are tender. Remove packs from grill, cut large X across top of each pack. Carefully fold back foil. Sprinkle potatoes with cheese; loosely close, and let stand 3 to 5 minutes or until cheese is melted. Garnish with green onions.