Preheat your oven to 400°F.

In a large mixing bowl, combine the ground chicken, breadcrumbs, Parmesan cheese, parsley, red onion, garlic, egg, oregano, salt, black pepper, and crushed red pepper flakes (if using).

Mix the ingredients together until well combined, but do not overmix.

Using your hands, form the mixture into meatballs, about 1 to 1.5 inches in diameter.

Heat the olive oil in a large oven-safe skillet over medium heat. Add the meatballs in batches, cooking until browned on all sides, about 5-7 minutes.

Once browned, transfer the skillet to the preheated oven and bake for 15-20 minutes, or until the meatballs are cooked through (internal temperature should reach 165°F).

Remove from the oven and let cool for a few minutes before serving.