In a nonstick skillet over medium-high heat, using the oil, cook chicken on both sides until nicely browned; arrange chicken on bottom of the slow cooker. Arrange the sliced onion around the chicken thighs.
In a medium size bowl mix together the remaining ingredients.
Pour the barbecue mixture over the chicken, cover, and cook for 4 – 5 hours on low or until chicken is almost fall off bone tender.
Layer a broiler pan with aluminum foil. Place the chicken on the foil and spoon some additional barbecue over the top. Place chicken about 8 inches below the element and broil on high until chicken starts to brown.
(Note: this recipe is very good even if you skip the broiler step)