Tunable optical elements are mostly realized by microelectromechanical systems, which require expensive and complex lithography during processing. We demonstrate an alternative device based on an electrically tunable microcavity employing a dielectric soft elastomer actuator. The cavity resonance is varied by changing the physical cavity thickness due to electrostriction of the soft elastomer. We realize a tunable metal-elastomer-distributed Bragg reflector multi-half wavelength microcavity with a cavity layer thickness around 12 μm and quality factors up to 700. Applying a voltage up to 60 V between bottom ITO and top metal electrode tunes the wavelength of the cavity modes up to Δλ=14 nm, which relates to a cavity thickness change of about 200 nm. This concept allows the implementation of tunable optical elements like tunable filters or resonators with low cost and simple processing.