01 - In a large mixing bowl, combine ground turkey, breadcrumbs, egg, parsley, garlic, grated onion, Parmesan, oregano, salt, and pepper. Mix gently with hands until just combined, avoiding overmixing.
02 - Shape the mixture into 16 golf ball-sized meatballs and place them on a tray.
03 - Heat 2 tablespoons olive oil in a large skillet over medium heat. Brown meatballs in batches, turning to brown all sides, about 5 minutes total. Remove meatballs to a plate.
04 - In the same skillet, add 2 tablespoons olive oil and sauté chopped onion until softened, approximately 3 to 4 minutes. Add garlic and cook for 1 minute.
05 - Stir in crushed tomatoes, dried basil, oregano, sugar, salt, and pepper. Bring the mixture to a simmer.
06 - Gently place the meatballs into the sauce. Cover and simmer over low heat for 20 to 25 minutes until meatballs are fully cooked and the sauce has thickened. Stir in fresh basil leaves if desired.
07 - Serve the meatballs hot over pasta, rice, or with crusty bread.