For each pound of chicken, it takes about 20 minutes under a covered grill. For example, a 5-pound whole chicken will take approximately 2 hours of cook time to have a fall off the bone tender chicken. However, the only true indicator that the chicken is fully cooked is when the internal thigh temperature of the chicken reaches 165º degrees F (or 73º degrees C). The juice of the chicken should run clear, and the chicken skin should be a beautiful bronze color.