Heat 1 tablespoon of vegetable oil in a large Dutch oven or heavy-bottomed pot over medium-high heat until shimmering.
Add the beef cubes in a single layer and cook for 5 to 7 minutes, turning occasionally, until browned on all sides.
Stir in the diced onion and minced garlic, cooking for 3 minutes until the onion is softened and fragrant.
Add the chopped carrots, celery, beef broth, diced tomatoes with their juices, dried oregano, bay leaf, salt, and pepper to the pot.
Bring the soup to a boil, then reduce the heat to low, cover the pot, and simmer gently for 45 minutes, allowing the flavors to meld and the beef to become tender.
Stir in the frozen green beans and frozen corn, and continue to simmer uncovered for an additional 15 minutes until the vegetables are heated through and tender.
Remove and discard the bay leaf, then taste the soup and adjust seasoning with more salt and pepper if needed before serving hot.
