Combine the parsley, ricotta, 1/4 cup Parmesan, the salt, oregano and pepper in a bowl. Add the onion and garlic mixture with the beef, breadcrumbs, eggs and carrots. Mix gently by hand, being careful not to over-mix.
Roll out 21 meatballs by hand and arrange on a baking sheet. Bake for 30 minutes. Meanwhile, heat the marinara sauce in a saucepan.
Arrange the meatballs on a platter and top with the marinara sauce and remaining Parmesan.