You can use any kind of potatoes but red potatoes come out delicious and are better for you (converted to sugar slower). Potatoes on the grill is the one recipe that is truly unique to the GFG and can't be duplicated cooking them any other way. They come out like a cross between potato chips and French fries.
Peel the potatoes and cut them into approximately 1/8 inch strips (You'll find your favorite thickness after you cook them a few times.)
Cover them with extra virgin olive oil or light olive oil.
Spread them across the grill and try not to overlap them too much. If you cut them a little thicker you'll fit more but you don't want to make 'em too thick. You can fit about 1 1/4 pounds on a family size grill.
Cook them for 27 to 30 minutes. Yes, that's a long time but they'll come out crispy moist that way.