Mix butter and garlic powder together.
Slice potatoes lengthwise in 1/4 inch slices. Coat potato slices with butter mixture and place on grill.
Grill each side for 3-4 minutes, watching carefully. Remove from the grill when potatoes are tender.
Sprinkle with seasoned salt immediately after removing from the grill. Serve with sour cream and ketchup, if desired.