Pat the beef dry with paper towels and season it with salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat. Brown the beef in batches for 2–3 minutes per side.
Transfer the browned beef to a 6-quart crockpot.
Add the diced onion and minced garlic to the same skillet. Cook for 1–2 minutes, then scrape up any browned bits from the bottom of the skillet.
Transfer the onion, garlic, and skillet juices to the crockpot.
Add the cubed potatoes, sliced carrots, celery, frozen green beans, frozen peas, and frozen corn.
Pour in the beef broth and add the diced tomatoes, tomato paste, Worcestershire sauce, dried thyme, Italian seasoning, bay leaves, salt, and black pepper.
Stir gently until the ingredients are evenly combined and mostly covered with broth.
Cover the crockpot and cook on LOW for 7–8 hours or HIGH for 4–5 hours, until the beef is tender and the vegetables are cooked.
Remove and discard the bay leaves.
Taste the soup and adjust the salt and black pepper as needed.
Stir in the chopped fresh parsley.
Ladle the beef vegetable soup into bowls and serve warm with crusty bread, biscuits, or crackers.