Heat the grill to medium.
Thinly slice the potatoes.
In a small bowl, mix salt, garlic powder and black pepper.
Toss the sliced potatoes with olive oil, liquid smoke and seasonings.
Prepare 4 large sheets of foil, preferably heavy duty, or double the regular foil.
Divide the potatoes between prepared foils.
Place the sliced garlic over the potatoes.
Close each packet tightly and grill on medium for 15-20 minutes, or until fork tender.
Carefully open the packets and immediately top the potatoes with cheese.
Let the cheese melt for a couple of minutes and serve immediately. If desired, sprinkle some scallions for garnish.