In a large heavy saucepan over medium-high heat, combine onions, carrots, mushrooms, broth, parsley, barley and pepper. Bring to boil, reduce heat and simmer, partly covered, 40 minutes or until barley is tender.
Mushroom-barley soup variations: For a slightly sharper taste, replace carrots with 2 sliced celery stalks and 1/2 red bell pepper, cored, seeded and chopped.