Heat the oil in a large heavy-based saucepan over a medium heat. Add the beef and sauté for about 5 minutes until browned all over. Remove the beef to a plate, using a draining spoon.
Add the onions to the pan and cook gently for 5 minutes, then stir in the mushrooms and cook for a further 3–4 minutes. Return the beef to the pan. Stir in the carrots, barley, stock, wine or tomato juice and seasoning and bring to the boil.
Reduce the heat, partially cover the pan and simmer for 1–1¼ hours or until the beef and barley are tender.
Stir in the peas and cook, uncovered, for 5 minutes. Add the lemon juice and season to taste.