In a large pot, heat the olive oil over medium-high heat. Add the beef stew meat and brown on all sides, about 5-7 minutes. Remove the beef and set aside.
In the same pot, add the chopped onion and garlic. Sauté for 2-3 minutes until the onion is translucent.
Add the carrots, celery, and bell pepper to the pot. Cook for another 5 minutes, stirring occasionally.
Return the browned beef to the pot. Stir in the diced tomatoes, beef broth, green beans, thyme, oregano, salt, and pepper. Add the diced potatoes and bay leaf.
Bring the mixture to a boil, then reduce the heat to low. Cover and simmer for 1.5 to 2 hours, or until the beef is tender. Stir occasionally and adjust seasoning as needed.
Remove the bay leaf before serving. Ladle the soup into bowls and enjoy!