A temperature-controlled and temperature-compensated oscillating device and a method of temperature control and temperature compensation is disclosed. The operating temperature of a frequency source is adjusted by driving a heater to a target temperature when the ambient temperature is in a first range between a first temperature and a second temperature higher than the third temperature. The frequency variation of the frequency source resulted from a variation of the ambient temperature is reduced by applying a voltage to the frequency source when the ambient temperature is in a second range between a third temperature and a fourth temperature higher than the third temperature. The third temperature is higher than the first temperature.