For multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems working in frequency and time selective (doubly selective) fading channels, the existence of intercarrier interference (ICI) will significantly degrade system performances. In this paper, by devising a so-called optimum group filtering processing, we propose an iterative soft interference cancellation based quasi-a posteriori probability (ISIC quasi-APP) detector which has a low complexity and significantly outperforms the conventional ISIC based minimum mean square filtering (ISIC MMSE) detector.