Peel away the outer dry leaves from head of garlic, leaving skin of garlic cloves intact. Using a knife, cut off about 1/4 inch of the pointed top portion of head, leaving the bulb intact but exposing individual cloves.
Place garlic head, cut side up, in a small baking dish; drizzle with oil. Bake, covered, in a 400 degrees oven for 25 to 35 minutes or until cloves feel soft when pressed. Cool slightly. Press garlic pulp from individual cloves; mash pulp with a fork.
In a large saucepan combine the mashed garlic pulp, Vegetable Stock, leeks, celery, basil, and black pepper. Bring to boiling; reduce heat. Simmer, covered, about 10 minutes or until leeks and celery are tender.
Stir in the tomatoes, zucchini, and barley. Return to boiling; reduce heat. Simmer, covered, about 10 minutes more or until barley is tender.