Preheat the grill to medium-high heat.
Thread the chicken, peppers, pineapple, and onion alternately onto the skewers.
Brush olive oil over the skewers and sprinkle with garlic powder, salt, and pepper.
Place skewers on the grill and cook for 10-15 minutes, turning occasionally, until chicken is cooked through.
During the last 5 minutes, brush barbecue sauce onto the skewers and grill until caramelized.
Remove from grill and serve hot with your favorite sides.