Preheat your oven to 400°F (200°C).
Lightly grease a 9x13-inch baking dish with oil or line with parchment for easy cleanup.
Prepare the peppers. Slice each bell pepper in half lengthwise through the stem, then gently remove seeds and membranes. Brush the cut sides with a little oil and season with a pinch of salt and pepper.
Soften the peppers.
Place pepper halves cut side up in the baking dish. Bake for 10–12 minutes to soften slightly. This step helps them cook through without getting watery.
Make the filling.
In a large bowl, mix shredded chicken, cream cheese, BBQ sauce, red onion, smoked paprika, garlic powder, onion powder, cumin (if using), and mozzarella or Monterey Jack. Season with salt and pepper. The mixture should be creamy and cohesive.
Optional veggie boost.
If using riced cauliflower, quickly sauté it in a skillet with a teaspoon of oil and a pinch of salt for 3–4 minutes to steam off moisture. Fold into the chicken mixture.
Stuff the peppers. Remove peppers from the oven.
Spoon the chicken filling evenly into each pepper half, gently mounding it. Sprinkle the cheddar over the top.
Bake until bubbly. Return the dish to the oven and bake for 15–18 minutes, until the peppers are tender and the cheese is melted and golden in spots.
Finish and serve.
Let cool for 5 minutes. Garnish with chopped cilantro or green onions. Add a squeeze of lime if you like a bright finish.