This paper proposes a novel receiver with virtual channels for overloaded MIMO systems, where the number of spatial multiplexing streams is more than that of receive antennas. We propose extended rotation matrices used for the receiver in order to make the receiver performance flexible in terms of complexity and detection performance. A lot of the extended rotation matrices can be formed, even if the size of the rotation matrix is fixed. This paper proposes to select the optimum extended rotation matrix adaptive to the overloaded MIMO channel for further performance improvement. The performance of the proposed receiver with the extended rotation matrix is evaluated by computer simulation. It is shown that the the optimum extended rotation matrix selection attains 2dB of a gain at BER of 1CP3 in the proposed receiver.