1. Line a four to six quart slow cooker with a liner bag or spray with cooking spray.
2. Rinse and pat chicken pieces dry.
3. Place chicken in slow cooker and season lightly with spices.
4. Combine barbecue sauce ingredients in a small bowl.
5. Spread onion slices over the chicken and top with sauce.
6. Cover and cook for five to six hours on low or three to four hours on high.