In large pot, heat oil over medium heat. Add celery, carrots, onion, bell pepper, and garlic. Cook for 1 to 2 minutes until slightly tender.
Add beef broth/stock, vegetable broth, thyme, and pepper to celery mixture. Bring to boil.
Add potatoes and steak and reduce heat until soup is constantly simmering. Cook for 15 to 20 minutes until potatoes are soft and steak is very tender.
Add steak sauce and mix well. Serve and enjoy!