Preheat your oven to 400°F (200°C).

In a large mixing bowl, combine the ground beef, breadcrumbs, Parmesan cheese, parsley, egg, garlic, oregano, salt, and pepper.

Using your hands, gently form the mixture into meatballs about the size of a golf ball.

Place the meatballs on a baking sheet lined with parchment paper and bake for 20 minutes.

While the meatballs are baking, heat the marinara sauce in a large skillet over medium heat.

Once the meatballs are done, add them to the skillet with the marinara sauce and let them simmer together for about 10 minutes.

Serve the meatballs hot, topped with more sauce and a sprinkle of Parmesan.