Preheat your oven to 400 degrees F. Line a baking sheet with parchment paper and set aside.
Add the turkey, egg, bread crumbs, Parmesan, olive oil, garlic, parsley, spinach, onion, salt, and pepper to a large mixing bowl. Mix everything together until evenly combined.
Use a cookie scoop (or greased hands) to portion 30 equal size meatballs. Grease your hands with a little oil and roll the meatballs so they are round. The turkey mixture will be soft. If they’re sticking, add a little more oil to your hands. Arrange the meatballs on the prepared baking sheet.
Bake for 10 minutes on the middle rack. Then turn your oven to broil and cook until the meatballs are golden brown and cooked through (165 degrees F internal temperature).
Remove the meatballs from the oven and transfer them to a serving bowl or use them for dinner. Serve warm.