Oscillator quick-startup circuit and method in which a voltage step is applied to a resonator (crystal) resulting in ringing which is amplified and fed into a locking circuit which locks to it, such as a programmable delay circuit. Once locking is complete, then the circuit is switched into a standalone oscillator mode, having a feedback path, the output of this injection oscillator energizes the resonator for achieving quick startup of a primary oscillator, in response to it automatically adjusting injection oscillator frequency to match the frequency of the resonator. A digital circuit controls the configuring of the circuit for applying the voltage step, adjusting the locking circuit, and then switching into a standalone oscillator mode.