2. Place the chicken in a large roasting pan.
3. Roughly chop two sprigs of the rosemary. In a small bowl, mix together Dijon mustard, honey, chopped rosemary, lemon juice and lemon zest.
4. Place the remaining sprig of rosemary, a lemon half, the onion quarters and garlic in the cavity of the bird. Using a pastry brush, coat the outside of the bird with the lemon honey glaze.
5. Place the roasting pan in the oven and baste the chicken every 15 minutes with any remaining glaze. Roast until a thermometer inserted into the thigh reaches 180° and juices run clear, about one hour. Remove and discard the skin. Serve hot or at room temperature.