Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper, if using.
In a large mixing bowl, combine the ground beef and ground pork.
Add the breadcrumbs, grated Parmesan cheese, chopped parsley, egg, minced garlic, dried oregano, salt, black pepper, and optional red pepper flakes to the meat mixture.
Mix well with your hands or a spoon until all ingredients are evenly combined.
Shape the mixture into meatballs, about 1.5 inches in diameter, and place them on the prepared baking sheet.
Optionally, in a frying pan over medium heat, brown the meatballs for 2-3 minutes on each side to add extra flavor.
Bake the meatballs in the preheated oven for 20-25 minutes, or until they reach an internal temperature of 160°F (70°C) and are cooked through.
Serve the meatballs with marinara sauce, either on a plate or in a sub, as desired.