Preheat oven to 400 degrees.
Arrange cut and de-seed peppers in a lightly greased baking dish.
Combine pre-cooked shredded chicken, mayonnaise, hot sauce, garlic powder, onion powder, salt, black pepper, and ¾ of the green onions. Mix thoroughly. Taste and add more hot sauce or salt if desired.
Fill peppers with buffalo chicken mixture - make sure to pack it in the pepper.
Cover the baking dish and bake for 30 minutes. Remove foil and bake another 20 minutes - until peppers are tender and the stuffing is bubbling and slightly browned.
Top with a drizzle of ranch dressing and the rest of the thinly sliced green onion