Scrub potatoes and set into a large pot filled with cold water. Bring to boil over high heat and cook for 8–10 minutes until they are partially cooked. (Overcooking here leads to a "mushy" texture after they are grilled. You are looking for a softened, but still firm, cook on the potatoes)

Drain potatoes and transfer to a bowl. Drizzle with olive oil. Add rosemary, and sprinkle with kosher salt to taste. Stir.

Add potatoes to hot grill (400°). Grill until golden and skins are crisp, approximately 10 minutes. Test to ensure the potatoes are soft and fully cooked through—insert a sharp knife to the centre to ensure they are soft.

Remove from grill back into the bowl, and stir to coat with a touch of olive oil and rosemary remaining in the bowl. Serve.