In a medium bowl, mix the turkey, egg, onion, and bread crumbs. Adjust the amount of bread crumbs as needed to make a stiff mixture. Season with salt and pepper. Transfer the mixture to a 9x5 inch loaf pan, and sprinkle with poultry seasoning.
Bake 1 1/2 hour in the preheated oven, or until meat is cooked through and the internal temperature is at least 170 degrees F (70 degrees C) when taken with a meat thermometer.