In a large bowl, toss potatoes with green pepper, onion and pepper; place in center of a greased 24x18-in. piece of heavy-duty foil. Fold foil around vegetables and crimp edges to seal., Grill, covered, over medium heat 15-20 minutes or until potatoes are tender. Remove from grill. Open foil carefully to allow steam to escape. Add ham; sprinkle with cheese. Grill opened packet, covered, 2-4 minutes longer or until cheese is melted.