Preheat oven to 350°F. Line a baking sheet with parchment paper, and coat with cooking spray.
In a large mixing bowl, add chicken, avocado oil, salt and pepper; toss to coat.
Add bell peppers, onion and barbecue sauce; stir to combine, and add to prepared baking sheet.
Bake 20 minutes, remove from oven and add pineapple. Return to oven, and bake another 10-15 minutes or until chicken is cooked through and vegetables are tender.
Garnish with cilantro and extra barbecue sauce, if desired.