This paper addresses the margin adaptive problem for the filter bank multicarrier (FBMC) modulation based on the offset QAM (OQAM), referred to as FBMC/OQAM. The analysis conducted in this paper reveals that due to the specific FBMC/OQAM transmission format the system has to deal with inter-user, inter-symbol and inter-carrier interference to solve the resource allocation problem. To manage the interference, the successive channel allocation method, originally proposed for the orthogonal frequency division multiplexing (OFDM), has been modified by organizing subcarriers in groups and assigning subcarriers to users in a block-wise fashion. Following this strategy and making some approximations we demonstrate that it is possible to pose a single problem that is valid for OFDM and FBMC/OQAM. In this case, numerical results show that FBMC/OQAM is more energy-efficient than OFDM because it requires less power to transmit the same information rate.