Prep the oven and peppers: Preheat the oven to 400°F (200°C). Slice the bell peppers in half lengthwise and remove seeds and membranes.
Brush the insides lightly with olive oil and season with a pinch of salt and pepper. Place them cut side up in a baking dish.
Par-bake the peppers: Bake the pepper halves for 10–12 minutes to soften slightly. This helps them cook through without getting soggy once stuffed.
Make the buffalo filling: In a skillet over medium heat, add the butter (if using).
Stir in the garlic and cook for 30 seconds until fragrant. Add the buffalo sauce, cream cheese, onion powder, and a pinch of pepper. Stir until smooth and creamy.
Stir in chicken and cheese: Add the shredded chicken and half of the cheddar.
Mix until everything is coated and warmed through. Taste and season with salt if needed.
Add dressing: Off the heat, fold in the ranch or blue cheese dressing. This rounds out the heat and gives the filling a rich, tangy finish.
Stuff the peppers: Spoon the buffalo chicken mixture evenly into the par-baked pepper halves.
Top with the remaining cheddar and, if you like, a sprinkle of blue cheese.
Bake to finish: Return the dish to the oven and bake for 12–15 minutes, until the cheese is melted and bubbling and the peppers are tender.
Garnish and serve: Let the peppers rest for 5 minutes. Sprinkle with green onions or chives. Serve with extra buffalo sauce and a drizzle of ranch or blue cheese dressing if you like more sauce.