In a large pot or Dutch oven, heat the olive oil over medium heat. Add the ground beef and cook until browned, breaking it apart with a wooden spoon. Drain excess fat if necessary.
Add the diced onion and minced garlic to the pot. Sauté for about 3-4 minutes until the onion becomes translucent.
Stir in the sliced carrots, celery, bell pepper, and potatoes. Cook for an additional 5 minutes, stirring occasionally.
Pour in the beef broth and add the canned diced tomatoes with their juice. Stir in the dried oregano, dried thyme, salt, and pepper.
Bring the mixture to a boil, then reduce the heat to low. Cover the pot and let it simmer for about 20 minutes, or until the vegetables are tender.
In the last five minutes of cooking, add the frozen green beans. Allow them to heat through.
Taste and adjust seasoning if needed. Serve hot, garnished with fresh parsley if desired.