In a large pot or Dutch oven, brown the ground beef over medium heat until fully cooked, about 5-7 minutes. Drain any excess fat.
Add the chopped onion and minced garlic to the pot with the ground beef. Cook for an additional 2-3 minutes until the onion is soft.
Add the diced carrots, celery, and bell pepper to the pot. Stir and cook for another 5 minutes until the vegetables begin to soften.
Stir in the canned diced tomatoes (with their juice), beef broth, diced potatoes, Worcestershire sauce, Italian seasoning, salt, and black pepper. Bring the mixture to a boil.
Reduce the heat to low and allow the soup to simmer covered for about 20 minutes or until the potatoes and carrots are tender.
If using, stir in the frozen green beans and cook for an additional 5 minutes.
Taste, and adjust seasoning with more salt and pepper if needed.
Ladle the soup into bowls and garnish with chopped fresh parsley if desired.