The computational complexity of MCS adaptation for linear and non-linear MU-MIMO can be reduced by avoiding QR decomposition during subsequent stages of MCS adaptation. For instance, QR decomposition can be avoided in later stages of MCS adaptation by computing an instant upper right triangular matrix (R1) directly from an earlier upper right triangular matrix (R) and an earlier unitary matrix (U), which were obtained during a previous stage of MCS adaptation. As such, the instant upper right triangular matrix (R1) is obtained without performing QR decomposition on an instant Hermitian matrix (H1H), thereby allowing MCS adaptation to be performed for the new user group with less complexity. Additionally, computational complexity of MCS adaptation for linear MU-MIMO can be further reduced by avoiding matrix inversion during subsequent stages of MCS adaptation.