In a bowl, combine ground beef, breadcrumbs, Parmesan, egg, garlic, oregano, salt, and pepper.
Mix until well combined, then form into small meatballs.
In a large pot, heat a bit of oil over medium heat.
Add the meatballs to the pot and brown on all sides, about 5 minutes.
Remove the meatballs and set aside.
In the same pot, add onion, carrots, and celery; sauté until softened.
Pour in the beef broth and bring to a boil.
Return the meatballs to the pot and reduce to a simmer.
Cook for an additional 15 minutes until meatballs are cooked through.
Serve hot, garnished with fresh parsley.