Preheat your oven to 375°F.
Cut the tops off the bell peppers and remove the seeds and membranes. Place the peppers upright in a baking dish.
In a large skillet over medium heat, cook the ground chicken until browned and cooked through, about 5-7 minutes. Drain any excess fat.
Add the buffalo sauce, diced celery, green onions, garlic powder, onion powder, salt, and pepper to the skillet. Stir to combine and cook for an additional 2-3 minutes until heated through.
Remove the skillet from heat and stir in half of the shredded cheddar cheese.
Stuff each bell pepper with the buffalo chicken mixture, pressing down gently to pack it in. Top each pepper with the remaining cheddar cheese.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and the peppers are tender.
Let the stuffed peppers cool for a few minutes before serving. Garnish with fresh parsley if desired.