Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper or lightly coat it with cooking spray.
In a large mixing bowl, combine the ground turkey, breadcrumbs, grated Parmesan cheese, chopped parsley, egg, minced garlic, onion powder, salt, black pepper, oregano, and red pepper flakes (if using).
Mix all the ingredients together until well blended, but be careful not to overmix as this can make the meatballs tough.
Using your hands, form the mixture into meatballs about 1 inch in diameter and place them on the prepared baking sheet, leaving space between each one.
Bake in the preheated oven for 20-25 minutes or until the meatballs are cooked through and reach an internal temperature of 165°F (75°C).
While the meatballs are baking, heat the marinara sauce in a large skillet or saucepan over medium heat.
Once the meatballs are done, add them to the marinara sauce and allow them to simmer for about 5 minutes to soak up the flavor.
Serve hot with spaghetti, in a sub sandwich, or on their own, garnished with extra parsley or Parmesan, if desired.