The IEEE 1609.4 standard has been proposed to provide multi-channel operations in wireless access for vehicular environments (WAVE), where all the channels are periodically synchronized into control and service intervals. In this paper, based on the concept of cognitive radio, the vehicles are categorized into primary providers (PPs) that intend to transmit safety-related messages and secondary providers (SPs) with non-safety information to be delivered. The cognitive radio- enabled optimal channel-hopping sequence (CROCS) approach is proposed to improve the channel utilization of IEEE 1609.4 standard for multi- channel vehicular networks. Prioritized channel access is analyzed in the CROCS scheme in order to increase the transmission opportunity of the PPs. Moreover, optimal channel-hopping sequence is assigned for the SPs based on the dynamic programming technique. It is designed to consider the optimal load balance between both the channel availability and channel utilization within the throughput constraints of PPs. With the adoption of proposed CROCS approach, simulation results show that maximum throughput of SPs can be achieved with guaranteed quality-of-service requirement for the PPs.