Step 1

Prepare the grill for direct cooking over high heat so it maintains a steady temperature of 500º F (260ºC).

Step 2

Pour the oil and garlic in a large flameproof roasting pan. Place the pan on the grill grate, close the lid, and let it heat until the oil begins to shimmer, about 2 minutes.

Step 3

Carefully add the potatoes to the pan and gently stir to coat with the oil. Close the lid on the grill and let the potatoes roast, keeping the lid closed except to occasionally turn the potatoes with a thin metal spatula, until they're golden brown and tender, 20 to 25 minutes.

Step 4

Season the potatoes to taste with salt and pepper and, if desired, a sprinkle of rosemary. Using a slotted spoon, move the potatoes into a bowl or platter and serve hot.