Abstract: A double oven crystal oscillator (DOCXO) is disclosed which is highly stable by incorporating means to reduce the effects of ambient pressure changes on the frequency of the oscillator. The oscillator crystal is mounted in a temperature controlled inner oven to reduce the effects on the frequency stability of the oscillator. The oscillator circuitry and all circuitry associated with the inner oven is mounted in good thermal contact with the inner oven. A Faraday shield at ground potential is placed over the oscillator circuitry to minimize the effects of stray capacitance between the oscillator components and the case wall of the inner oven. The effects of minor deformations in the case walls within the oscillator caused by ambient pressure changes and other factors causing pressure changes are thereby greatly minimized.