Preheat your oven to 375°F.
In a large skillet over medium heat, cook the ground chicken until browned and fully cooked, about 5-7 minutes.
Stir in 1/2 cup of buffalo sauce, garlic powder, onion powder, salt, and pepper. Mix well and cook for an additional 2-3 minutes.
While the chicken is cooking, prepare the bell peppers by cutting the tops off and removing the seeds.
In a large bowl, combine the cooked chicken mixture with diced celery and green onions.
Stuff each bell pepper with the chicken mixture, pressing down gently to pack it in.
If using, sprinkle shredded cheddar cheese on top of each stuffed pepper.
Place the stuffed peppers in a baking dish and pour the remaining buffalo sauce over them.
Cover the dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10 minutes, or until the peppers are tender and the cheese is bubbly.
Garnish with fresh parsley if desired and serve hot.