Preheat the oven to 375°F. Prepare a baking tray by lining it with parchment paper or lightly greasing the surface with oil.
In a large mixing bowl, thoroughly combine the ground turkey, chopped mushrooms, onion, celery, cranberries, cornmeal or stuffing mix, egg, and seasonings. Mix until all components are evenly incorporated.
Using a scoop or melon baller, portion the mixture into 24 meatballs, approximately 1½ inches in diameter. Although the mixture will be quite moist, each ball should maintain its form when placed onto the baking sheet. Space each meatball at least one inch apart.
Bake without covering for 18 to 22 minutes, or until the internal temperature reaches 165°F as measured by a meat thermometer.
Serve warm, optionally garnished with fresh chopped parsley for color. These pair well with cranberry sauce for dipping or can be served on cocktail skewers for convenient presentation.