Combine lentils, barley, and broth in a large stock pot. Bring mixture to a boil, reduce heat, and simmer covered for 30 minutes.
In a non-stick skillet, sauté beef and onions over medium-high heat, breaking up with spoon, until beef is no longer pink, about 5 minutes. Add to stockpot along with the remaining ingredients. Bring to a boil, reduce heat and simmer, covered 20 to 30 minutes, or until vegetables are tender, stirring occasionally. Remove bay leaf before serving.
Makes 6-8 servings.