Preheat oven to 200ºC (390ºF) Place the rosemary, garlic, oil, salt and pepper in a bowl and stir to combine. Place the chicken and onions in a baking dish and pour over the rosemary mixture. Roast for 30 minutes. Add lentils, olives and stock and cook for a further 30 minutes or until chicken is golden and cooked through. Serves 4.