Heat gas or charcoal grill. If potatoes ar large, cut in half or quarter for uniform pieces. Place potatoes in an 8 " square disposable foil pan.
In small bowl, mix butter, garlic and salt together. Pour over potatoes. Cover pan with foil.
When grill is heated, place potatoes on gas grill over medium heat or on charcoal grill over medium coals. Cook 35 - 45 minutes or until potatoes are tender, stirring potatoes several times during cooking.
Could also make a foil pocket and seal tightly and turn over several times during cooking.