Brown beef and onion in a 6-quart pot over medium-high heat for 8 minutes, breaking beef into small crumbles and cooking it to 160°F. Drain excess fat.
Add carrots and garlic and cook for 2 minutes, stirring from the bottom.
Add tomatoes, broth, thyme, Worcestershire, salt and pepper. Cover and bring to a simmer.
Stir in quick-cooking barley and green beans. Simmer partly covered for 10 to 12 minutes until barley and carrots are tender, stirring once or twice.
Divide among 6 bowls with broth surrounding the beef, vegetables and grains.