Heat the olive oil in a large pot or Dutch oven over medium heat. Add the cubed beef and brown on all sides, about 5-7 minutes. Remove the beef and set aside.
In the same pot, add the diced onion and minced garlic. Sauté until the onion becomes translucent, about 3-4 minutes.
Add the sliced carrots and diced celery to the pot. Cook for another 3-4 minutes until the vegetables soften.
Return the browned beef to the pot. Add the diced potato, green beans, diced tomatoes (with juice), beef broth, dried thyme, dried oregano, and bay leaf.
Bring the mixture to a boil. Reduce the heat to low, cover the pot, and let it simmer for about 30 minutes, or until the beef and vegetables are tender.
Season with salt and pepper to taste. Remove the bay leaf before serving.
Ladle the soup into bowls and garnish with fresh chopped parsley, if desired.