Preheat oven to 180°C/350°F/Gas Mark 4. Crease a ceramic or roasting dish with olive oil or butter. Place barley in dish and scatter over leek, onions, carrot, garlic, herbs, and salt and pepper.
Cut chicken legs in two at the knee joint. Place on top of vegetables, trying not to overlap. Pour on the boiling stock, which ideally should cover the barley by 1 cm(½ in) – add a little more if necessary. Cover dish with foil and bake 30 minutes in the middle of the oven. Remove the cover and continue baking until chicken is cooked (juices run clear). Place under grill to colour chicken lightly, then serve.