IEEE 802.16, also called WiMAX was developed to accommodate large coverage and high bandwidth last-mile Internet access. In WiMAX, provisioning of QoS is still an important issue. Before transmitting packets, subscriber stations (SS) must send a bandwidth request message to the base station (BS). If available bandwidth is not sufficient to use unicast polling for each SS to send bandwidth request, the BS will form a group of stations that utilize multicast and broadcast polling to contend the slots for transmitting bandwidth request. Since extended real-time polling service (ertPS) proposed in 802.16e has strict delay time requirement, the lower the delay, the better the QoS. In order to reducing the delay caused by collisions of request packets, we proposed a scheme that utilizes contention-free period to allocate slots for bandwidth request. Both mathematic analysis and simulation results show that our scheme features lower delay and better QoS performance for ertPS flows as the number of stations increases.