Wash chicken and remove excess fat. Leave skin on. Put in large bowl.
Sprinkle with salt, pepper, and garlic powder. Mix seasoning into chicken by hand so you can knead the spices in meat.
Add celery, onion and bell pepper. Mix that by hand also. Cover bowl with foil or put contents of bowl in a large ziplock bag.
Refrigerate bag for at least 2 hours... I have mixed a complete 10# of chicken and divided it in 2 ziplock bags and froze them for several months. When ready to use thaw a bag and go to step 5.
Place each piece in a baking dish. They can be placed in tight and touching. Then pour the bell pepper and celery and any small pieces of onion from the bag on top of the chicken.
Cover with aluminum foil and bake at 350 for 1 hour and 15 minutes. Uncover and cook an additional 15 minutes.
Remove from oven and cover with foil to keep it from drying until you serve it..