Place soup bones and water in a Dutch oven or soup kettle. Slowly bring to a boil. Reduce heat; cover and simmer for 2 hours.
Set beef bones aside until cool enough to handle. Remove meat from bones; discard bones and return meat to broth. Add the potatoes, carrots, onion, barley, tomatoes, salt, pepper, garlic and bay leaf if desired. Cover and simmer for 50-60 minutes or until vegetables and barley are tender.
Discard bay leaf. Combine cornstarch and cold water until smooth; stir into stew. Bring to a boil; cook and stir for 2 minutes or until thickened. Yield: 10 servings.