Add olive oil, minced garlic, salt, and thyme or rosemary. Toss well to coat.
Lay out two double layers of aluminum foil (four total sheets), about 12"x12" in size. You will want to use a double layer of foil so that it doesn't tear during cooking.
Evenly distribute the potatoes between the two pairs of foil. Fold the foil up around the potatoes and seal well.
Place on a medium to high heat area of a campfire or other grill and cook for 30-40 minutes until the potatoes are tender.
Be careful when opening the packets as you don't want to get burned by the steam.
Notes
It is super easy to prepare packets in advance for camping or to cook over a grill in your own backyard.