PREHEAT grill to 400°F. COMBINE potatoes, onion and garlic in a large bowl. Drizzle on oil and set aside. Combine curry powder, cumin, chili powder and turmeric. Pour spice mixture over potato mixture. Stir evenly to fully coat.
CENTER potatoes evenly in a single layer on a 12x24-inch sheet of Reynolds Wrap® Non-Stick Foil with non-stick (dull) side toward food. Season with salt and pepper to taste.
BRING up foil sides. Double-fold top and ends to seal, making one large foil packet, leaving room for heat circulation inside.
GRILL 15 to 20 minutes in covered grill, or until potatoes are tender. Garnish with fresh cilantro and serve immediately.