In a large mixing bowl, combine ground beef, breadcrumbs, Parmesan cheese, egg, minced garlic, dried oregano, salt, and black pepper.

Shape the mixture into balls about 1 inch in diameter.

In a skillet, heat olive oil over medium heat.

Add the meatballs to the skillet in a single layer and cook for about 5 minutes, turning occasionally until browned on all sides.

Pour the marinara sauce over the browned meatballs.

Reduce the heat to low, cover the skillet, and let the meatballs simmer in the sauce for 20 minutes.

Check that the internal temperature of the meatballs reaches 160°F.

Once cooked, serve the meatballs hot over pasta or as is.