This paper presents a one-chip temperature control for an OCXO application with a quartz crystal directly mounted on a CMOS chip. The design of this chip can reduce the size of an entire OCXO package dramatically since no separate PCBs are required for the oscillator, controller, and resonator. The reduced package size leads to less power consumption (303 mW at steady state) and a shorter warm-up time (190 seconds at room temperature). The temperature and frequency stabilities are 0.17 degC and 0.7 ppm respectively in the 0 degC to 60 degC external temperature range