Heat the oil in a large saucepan over medium heat. Add leek; cook 20 minutes or until tender and golden, stirring occasionally. Add mushrooms; cook 5 minutes or until tender, stirring occasionally. Add barley, salt, and pepper; cook 1 minute, stirring constantly. Add broth; bring to a boil. Cover, reduce heat, and simmer 30 minutes, stirring occasionally. Uncover and cook 5 minutes or until liquid is absorbed. Stir in parsley.