Roughly chop up the onions, green peppers, celery and garlic. Add to food processor and pulse until chopped up (not too fine, but not chunky). Add all these ingredients to a dutch oven with a little vegetable oil in bottom. Saute until soft.
Cut your oysters in half and keep juices generated by this. Add oysters (without juices) to the dutch oven and parsley. Allow to cook for about 5 minutes.
Turn off fire and add bread crumbs until the mixture is not wet but not dry. Keep adding bread crumbs until the consistency is reached. If you make it too dry, you can use the oyster juice.
Add onion and garlic powder to taste, along with salt and pepper. Add 1 egg, slightly beaten to mixture.
Add mixture to a 13 by 9 inch Pyrex bowl and smooth out the top. Adding a thin layer of bread crumbs on top along with thin slices of butter.
At this point, you can freeze them for future use of put in oven at 350 degrees and cook for about 30 minutes.