The GPM Ground Validation Conical Scanning Millimeter-wave Imaging Radiometer (COSMIR) GCPEx dataset used the Conical Scanning Millimeter-wave Imaging Radiometer (CoSMIR), which was utilized for the GPM Cold-season Precipitation Experiment (GCPEx) as an airborne high-frequency simulator of the GPM Microwave Imager (GMI), which was launched in 2014. The CoSMIR was modified with a new scan mode to acquire both conical and cross-track scan data simultaneously in a given flight satisfying the requirements of the Precipitation Measurement Mission (PMM) algorithm development team. The dataset provides well-calibrated radiometric data from 9 channels between 50-183 GHz with the accuracy on the order of +-1K. All channels besides the 89 and 165.5 GHz are horizontally polarized.