Prep your grill for indirect heat.
Lay out a sheet of heavy duty aluminum foil approximately 15-18 inches long.
Place the potatoes, onion, garlic, salt and pepper onto the foil sheet and drizzle with olive oil. Mix together with your hands.
Fold tinfoil into a packet, carefully sealing the seams.
Grill for 40 minutes, flipping periodically.
While the potatoes grill mix together butter, lemon zest and some pepper into a compound butter.
Carefully open the foil packet, the steam will be hot. Dot with the compound butter, squeeze on a splash of lemon juice and sprinkle on the chives.