Prepare the meatball mixture by combining ground beef, breadcrumbs, Parmesan cheese, egg, garlic, oregano, salt, and pepper in a bowl.
Shape the mixture into meatballs, about 1-inch in diameter.
Heat a skillet over medium heat and add a small amount of oil. Sear the meatballs until browned on all sides, about 5 minutes.
In a large pot, add beef broth, diced tomatoes, carrots, and celery, then bring to a simmer over medium-high heat.
Once simmering, gently add the seared meatballs to the pot and reduce the heat to low.
Cover and cook on low for about 20 minutes, allowing the flavors to meld and the meatballs to cook through.
Taste and adjust seasoning, adding salt and pepper as needed.
Serve hot, garnished with fresh parsley.