Place potatoes and celery in a large pot of water. Bring to a boil over high heat. Reduce to medium heat and simmer 15 minutes or until potatoes are tender. Drain and return to pot.
In a medium bowl, combine soup, sour cream, parsley, garlic powder, salt and pepper.
Stir soup mixture, half the bacon and half the onions into potato mixture. Spoon into a greased 2-quart casserole. Microwave on HIGH for 5 minutes.
Sprinkle remaining bacon and onions over the top of the dish and microwave on HIGH for 2 minutes more.