Place the chicken on a tray and drizzle with oil, season with salt and pepper, rosemary and lemon zest.
Make the crust by placing the chips in a food processor and pulsing until the chips are a fine crumb. Add the remaining ingredients and mix.
Prepare the barbeque for indirect cooking by turning one side of the barbeque to medium heat (325°F/160°C) and leaving the other side off.
Place a drip pan under the grill of the side without any heat.
Oil the grill well to help prevent sticking.
Place the chicken skin side down directly over the heat and cook without turning for 6-7 minutes or until the skin is crispy.
Flip chicken and move the legs to the side of the barbeque with no any heat.
Place a heaping spoonful of the crust topping on the cooked surface of the chicken and pat down to secure it in place.
Close the lid of the grill and cook for 15 minutes.
When the chicken is cooked remove from the grill and serve.