In a large bowl, toss together all ingredients until sweet potatoes are evenly coated with oil and spices.
Tear out four 12” x 12” sheets of heavy-duty tin-foil. Place ¼ of the potatoes in the center of each sheet of tin foil. To create foil packets, carefully fold in the left and right side of the square. Next, bring together the top and bottom of the square and tightly pinch to form a packet. Tip: Be sure to leave a bit of room for steam.
Place packets on the grill and cook for 5-7 minutes per side.