In this paper, a Ka-band CMOS push-push voltage- controlled oscillator (VCO) integrated into a glass-integrated passive device (GIPD) process is presented. The transformer, λ/4 transmission line, and inductors of the VCO are realized in the GIPD process, achieving superior performances, and therefore improve the phase noise of the VCO. Moreover, the transformer-based VCO is a differential Hartley topology to further reduce the phase noise and chip area. Operating at 1.8 V supply voltage, the VCO core consumes merely 3.8 mW of dc power. The measured phase noise is -109.18 dBc/Hz at 1 MHz offset from the 30.84 GHz oscillation frequency. The push-push VCO also demonstrates a 24.5 dB fundamental rejection, and exhibits an 8.4% tuning range. Compared with recently published CMOS-based VCOs, it is observed that the proposed VCO exhibits excellent performance under low power consumption.