In a frying pan, add Parkay, onion, celery, and parsley. Heat on medium heat with lid on for 10 minutes, stirring after first 5 minutes. Spray a 2 qt. casserole with Pam. Put filling bread in a mixing bowl and add the onion/celery/parsley mixture and mix with your hands. Add the eggs and milk and continue mixing with your hands. Pour everything into the casserole dish and pat it down with your hands. Bake at 375 degrees for 30-35 minutes with the lid on. Bake until it's slightly brown.
If you're making this for stuffing for turkey dinner, once everything is mixed you can stuff it inside the turkey before baking (you can double the recipe if you're using a big turkey).