Preheat oven to 350°F
Spray a 9×13 baking dish with cooking spray
Scatter quartered biscuit pieces evenly in the dish
Add BBQ sauce evenly
Layer half the cheese
Sprinkle chicken evenly
Add chopped onion if using
Sprinkle remaining cheese on top
Bake uncovered for 30–35 minutes until biscuits are cooked through and cheese is bubbly
If the top browns too quickly, loosely cover with foil and continue baking
Let rest 5 minutes before serving
Finish with chopped cilantro if desired
