1. Preheat grill to high heat.
2. Combine oil and chicken; toss to coat. Sprinkle chicken with pepper and salt. Place chicken on grill rack coated with cooking spray, and grill 6 minutes or until well-marked. Place 1 cup Rhubarb-BQ Sauce in a large bowl. Add chicken to bowl, tossing to coat chicken. Return chicken to grill; cook, turning and brushing with sauce from the bowl until glossy and caramelized, about 12 minutes.