Combine beef, stock, onions, and thyme in soup kettle. Simmer over low heat, partially covered, 2 hours. Skim occasionally. Remove beef, cool, cut meat from bones, and set aside. Cool broth, then chill and skim. Return broth and meat to kettle. Heat to simmer. Add remaining ingredients, simmer, partially covered, 20 minutes or until vegetables are tender, and serve hot.