This paper presents a low-power, low-phase noise class-C Bulk Acoustic Wave (BAW) oscillator. It achieves a FOM of −206.5 dB at 1 kHz offset, enabling low-power, crystal-less SoC implementation for multiple wireless standards. A reference oscillator module for SoC integration is presented with a corresponding optimal tuning procedure for best phase noise performance. Power efficient class-C operation, reduced device count, and amplitude trimming, allow for 3 dB $FOM$ and $FOM_{Q}$ improvement over state-of-the-art GHz MEMS-based oscillators.