In a large mixing bowl, combine the ground beef, ground pork, breadcrumbs, Parmesan cheese, milk, egg, garlic, parsley, salt, pepper, onion powder, oregano, and red pepper flakes. Mix everything together until just combined—be careful not to overmix, as that can make the meatballs tough.
Using a spoon or your hands, scoop out portions of the mixture and roll them into 1 to 1.5-inch meatballs. Place them on a parchment-lined baking sheet or plate.
You can bake or pan-fry these meatballs:
Baking: Preheat oven to 400°F. Place meatballs on a lined baking sheet and bake for 18-20 minutes until golden brown and cooked through.
Pan-Frying: Heat 2 tbsp olive oil in a large skillet over medium heat. Cook meatballs in batches, turning occasionally, for 8-10 minutes until browned on all sides and fully cooked.
Serve immediately with marinara sauce, pasta, or as an appetizer with toothpicks. Enjoy!