— Multicast and broadcast service (MBS) is one of the important services for next generation wireless systems. In WiMAX, the radio resource unit (i.e., time, frequency, code, etc.) for MBS is centralized allocated by a network device named Anchor ASN-GW. The ASN-GW has to ensure that non-overlapping radio resource units are allocated to BSs for delivering different MBS contents. This paper presents a method to allocate radio resource units in overlapping MBS Zones. We proposed radio resource allocation and re-allocation algorithms to minimize the number of re-allocated resource unit due to the change of MBS Zones topology. Simulation result shows that the proposed algorithms can reduce the number of re-allocations and thus, reduce the signaling message exchanged in the air interface and the core network. Keywords- multicast and broadcast service (MBS), multimedia broadcast/multicast service (MBMS), radio resource allocation