We present Multi-Channel Beacon (MCB), a novel approach for efficient wide area data dissemination in vehicular networks using all the DSRC/WAVE channels. Current standardization efforts towards beaconing (i.e., one-hop broadcasting) protocols in vehicular networks focus on the use of a single radio channel only. This is a major bottleneck at high vehicle densities, leading to high delays or packet loss. Instead, the main focus has been to use adaptive transmit rates in order not to overload the wireless channel. Based on our previous work towards multi-channel operation, we developed a novel approach, MCB, which provides adaptivity not only in time, i.e., congestion control, but also in space by selecting appropriate channels for upcoming data transmissions. We evaluated our approach in simulations, comparing our solution to state of the art beaconing protocols, most importantly to the current ETSI Decentralized Congestion Control (DCC) standard. Our results clearly demonstrate the feasibility of our multi-channel approach, showing that it successfully reduces channel utilization and observed packet collisions without sacrificing goodput.