Heat the oil in a large saucepan, add the onion, garlic, rosemary, carrots, parsnips and swede and cook over a low heat, stirring frequently, for 10 minutes.
Stir in the barley, beer or lager, stock and salt and pepper and bring to the boil. Reduce the heat, cover and simmer gently for 40–45 minutes until the barley and vegetables are tender. Stir in the parsley and adjust the seasoning. Serve with plenty of crusty bread.