Preheat your oven to 400°F (200°C). This ensures your meatballs will cook evenly and develop a nice crust.
In a large mixing bowl, combine the ground beef, ground pork, breadcrumbs, Parmesan cheese, parsley, egg, minced garlic, oregano, salt, black pepper, and red pepper flakes. Mix gently until well combined without overmixing.
Using your hands, scoop out about 2 tablespoons of the meat mixture and roll it into a ball. Place each meatball on a baking sheet lined with parchment paper. Repeat until all mixture is formed into meatballs.
Bake the meatballs in the preheated oven for about 20 minutes or until they are browned and cooked through. Check that the internal temperature reaches 160°F (71°C).
While the meatballs bake, heat a skillet over medium heat and pour in the marinara sauce. Once meatballs are done baking, transfer them carefully to the skillet with the sauce. Let simmer for 10-15 minutes to meld flavors.
Once the meatballs are well-coated in sauce, serve them with spaghetti, in a sub sandwich, or on their own with extra Parmesan and fresh herbs. Enjoy!