With the growth of multimedia traffic over mobile networks, multicast becomes one of more effective transmission approaches to be widely considered. The Multimedia Broadcast multicast service Single Frequency Network (MBSFN) has been introduced for long term evolution to improve signal-to-interference-plus-noise ratio at the cell edges, while selecting efficient modulation and coding schemes (MCS) for transmission is still an open issue. Unlike existing solutions in literature, the opportunistic multicasting concept is adopted in this work to aggressively enhance the spectrum efficiency (SE) of single frequency networks. Based on the derived model of effective SE in extended MCS adaptation intervals, we propose a statistical feedback-based approach to achieve opportunistic multicasting in MBSFN. The algorithm carefully selects the MCS complying with the adaptation need for channel quality changes and enabling high bottleneck user SE under reduced feedbacks. Comparing with other schemes for a single stream setup, the simulations show up to 340% higher SE over non-opportunistic method and 25% over the second best method maximizing the average SE. The number of successfully transmitted streams in a multi-stream scenario increased by 250% over the non-opportunistic approach and 40% over the average SE maximizing approach.