Preheat the oven to 375°F (190°C).
Prepare the bell peppers by slicing the tops off and removing seeds.
In a mixing bowl, combine the shredded chicken, buffalo sauce, cream cheese, cheddar cheese, green onions, garlic powder, salt, and pepper.
Stuff each pepper with the buffalo chicken mixture, pressing down to pack it tightly.
Place the stuffed peppers upright in a baking dish and cover with foil.
Bake in the preheated oven for 25-30 minutes.
Remove the foil and bake for an additional 5-10 minutes for a golden top.
Allow to cool slightly before serving.