As mobile devices, such as smart phones and tablet PCs, become more and more ubiquitous, it is increasingly popular for users to watch online video streaming on their mobile devices. Because of the nature of wireless broadcast, a wireless router (e.g., an access point or cellular tower) can retrieve video streams from the video server and then efficiently multicast them via wireless medium to multiple clients who are interested in those videos. However, clients could locate in different positions and therefore experience various wireless channel conditions. In addition, clients might be interested in different video content so that different video clips could have various popularity. The heterogeneity in wireless conditions and user interests makes bandwidth allocation in a wireless router for video multicast a challenging problem. In this paper, we propose a marginal-utility-based video multicast scheme that takes variant channel qualities and heterogeneous user interests into account. Our evaluation shows that, compared to interest-oblivious multicast, the proposed interest-aware approach can improve the average visual quality by up to 9 dB.