Put the quail into a bowl, sprinkle with the oil and rosemary, cover with cling film and marinate in the fridge for 20 minutes.
Meanwhile, in a pan, melt the butter. Add the leek and cook gently until soft, without browning. Add the pearl barley and stir to cover with the butter. Add enough stock to cover the barley and bring to the boil.
Keep cooking and adding stock for 25-30 minutes, until the barley is soft and plump but with a little bite. Season to taste with salt and pepper.
Preheat a barbecue or heat a grill to high. Thread the quail onto metal skewers and season with salt and pepper. Cook it on the barbecue or under the grill for about five minutes on each side, or until cooked through.
Serve the quail skewers with the pearl barley and salad.