1. Preheat grill to medium heat
2. In a large bowl add potatoes, garlic, olive oil, rosemary, and salt and pepper.
3. Toss to marinate.
4. Pour the potato onto a two layered sheet of heavy duty tin foil and add a sprig of rosemary and fold close.
5. Place on the grill for about 30 minutes, turning once half way through.
6. Before serving cut an X on top of the foil to release any steam and carefully open and serve.