Real-time video disseminations over wireless links such as video telephony, video conferencing and mobile TV have become fast growing applications. In order to cope with the increasing users' demand, a new scalable and efficient wireless distribution platform is needed. With numerous advantages such as QoS assurance, high data rate and wide coverage, WiMAX has been regarded as an ideal choice to provide ubiquitous access for multimedia applications. However, how to achieve effective layered video multicasting in WiMAX networks is a challenging issue. In this study, we propose a utility-based resource allocation mechanism for layered video multicasting. In the proposed approach, Application-Layer Forward Error Correction (AL-FEC) is employed to deal with inevitable packet loss. Thus, for each video layer, WiMAX base stations can jointly choose a proper Modulation-and-Coding Scheme (MCS) and AL-FEC overheads to transmit. Our goal is to maximize the system utility which comprises two important factors, system reward and resource usage. System reward represents the summation of video quality of all subscribers while resource usage denotes the consumed WiMAX resources in terms of time slots. To efficiently obtain the optimal solution, we propose two heuristic algorithms, namely genetic algorithm and Layered Policy Iteration (LPI) algorithm and compared their performance to the optimal solution found by exhaustive search. We demonstrate the performance of the approaches via extensive simulations. The simulation results show that the LPI algorithm can provide great service quality and utilize system resource effectively.