Wash and dry potatoes. Cut a small portion off the long side of the potato, lay this flat side down on a cutting board. Cut slices all the way across the length of the potato, slices should be 1/4-inch part from each other. Do not slice the potatoes all of the way through. Slice them until they are about 3/8-inch from the bottom of the potato. Slice all four potatoes in a similar fashion. Melt butter and stir in chopped garlic. Place each potato onto foil sheet. Nest the foil around the potato, this way the butter will stay in the foil pouch. Brush the butter onto each of the potatoes. Leave approximately half of the butter to brush over potatoes half way into the cooking process. I leave the potato unwrapped on the top portion of the potato. This way the potato gets an opportunity to get nice and crispy.
You will need to have your grill to at least 350 degrees. Medium sized potatoes take about 45 minutes until they are done. If your potatoes are larger it make take slightly longer before they are done. When you remove them from the grill season with salt and black pepper.