Heat the olive oil in a large soup pot or Dutch oven over medium-high heat. Add the lean ground beef and diced onion, then cook for 5–7 minutes while breaking the beef into small pieces, until the beef is browned and the onion is softened.

Drain excess fat from the pot if necessary. Add the minced garlic and cook for about 30 seconds, stirring constantly, until fragrant but not browned.

Stir in the carrots, celery, potatoes, beef broth, diced tomatoes with their juices, tomato sauce, Italian seasoning, salt, black pepper, and optional bay leaf. Mix well so the vegetables and seasonings are evenly distributed.

Bring the soup to a boil, then reduce the heat to a gentle simmer. Partially cover the pot and cook for 20–25 minutes, or until the potatoes and carrots are tender when pierced with a fork.

Stir in the frozen green beans and frozen corn. Simmer uncovered or partially covered for another 5–10 minutes, just until the frozen vegetables are heated through and remain pleasantly tender.

Remove the bay leaf before serving. Taste the soup and adjust the salt and black pepper as needed, then ladle it into bowls and serve hot.