In this paper we present a low-complexity MIMO-OFDM system based on adaptive signal combining in radio-frequency (RF). The limitations of the proposed architecture require the development of specific transmission and reception schemes. Specifically, we consider the problem of selecting the transmit and receive RF weights (beamformers), as well as the time and frequency linear precoders, under the assumption of i.i.d. Rayleigh channels perfectly known at the receiver side. The transmission scheme is based on orthogonal beam division multiplexing (OBDM) and minimum MSE beamforming, i.e., the data is sequentially transmitted by means of different transmit beamformers, whereas the receive beamformers are selected to minimize the MSE of the linear MMSE receiver. Finally, the performance of the proposed transmission scheme is illustrated by means of Monte Carlo simulations.