In a saucepan, combine the barley and 3 cups of vegetable stock. Bring to a boil over medium heat, cover, and simmer for 1 hour, or until the liquid is absorbed.
Meanwhile, heat the oil in a large pot and add the onion, carrots, celery, and mushrooms. Cover and cook the vegetables for about 5 minutes, until they begin to soften.
Add the remaining vegetable stock and simmer 30 minutes, covered.
Add the barley and simmer 5 minutes more. Add salt to taste and ladle into bowls. Serve garnished with chopped fresh parsley.
