In a large pot, heat the olive oil over medium heat. Sauté the chopped onion and minced garlic until they soften.
Stir in the carrots, celery, green bell pepper, cooked beef, beef broth, diced tomatoes with their juices, barley, Worcestershire sauce, thyme, bay leaf, and beef gravy mix. Bring the mixture to a boil.
Once boiling, lower the heat and cover the pot. Allow it to simmer for about 40-50 minutes, or until the barley is tender.
Remove the bay leaf and season the soup with salt and black pepper to taste. Stir in red wine, if using, and garnish with chopped parsley before serving.