In a large bowl, combine the ground turkey, breadcrumbs, Parmesan cheese, parsley, egg, garlic, onion powder, oregano, salt, black pepper, and red pepper flakes (if using). Mix until just combined, being careful not to overmix.
Preheat the oven to 400°F.
Form the mixture into meatballs, about 1 to 1.5 inches in diameter, and place them on a baking sheet lined with parchment paper.
Drizzle the olive oil over the meatballs. Bake in the preheated oven for 20-25 minutes, or until the meatballs are cooked through and golden brown.
While the meatballs are baking, heat the marinara sauce in a saucepan over medium heat until warmed through.
Once the meatballs are done, add them to the marinara sauce and simmer for an additional 5 minutes to absorb the flavors.
Serve the meatballs with pasta, on a sub roll, or over rice, and garnish with extra parsley and Parmesan if desired.