Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large mixing bowl, combine the ground turkey, breadcrumbs, Parmesan cheese, chopped parsley, minced garlic, egg, oregano, salt, black pepper, and red pepper flakes (if using).
Mix well using your hands or a spoon until all ingredients are fully incorporated, being careful not to overmix.
Using your hands, form the mixture into meatballs, about 1 to 1.5 inches in diameter, and place them on the prepared baking sheet.
Bake in the preheated oven for 20-25 minutes, or until the meatballs are cooked through and golden brown on the outside.
While the meatballs are baking, heat the marinara sauce in a small saucepan over low heat.
Once the meatballs are done, remove them from the oven and let them rest for a few minutes.
Serve the meatballs drizzled with warm marinara sauce and garnished with extra parsley, if desired.