Brown the beef: Heat olive oil in a large pot over medium heat. Add beef cubes in batches and sear until browned on all sides. Remove and set aside.
Sauté aromatics: In the same pot, add chopped onions, garlic, carrots, and celery. Cook for 5 minutes until softened and fragrant.
Build the base: Stir in tomato paste and cook for another minute to deepen the flavor. Add diced tomatoes, beef broth, thyme, bay leaf, salt, and pepper. Mix well.
Simmer slowly: Return the browned beef to the pot. Bring to a boil, then reduce heat to low. Cover and let it simmer for about 1 ½ to 2 hours, stirring occasionally until the beef is tender.
Add vegetables: Add potatoes, green beans, and corn. Simmer another 20–25 minutes, until all vegetables are cooked and the soup thickens slightly.
Taste and finish: Adjust seasoning if needed. Remove bay leaf, sprinkle with chopped parsley, and serve hot.