We perform a linear analysis to examine electric-field-induced stability of a thin film that caps a liquid layer resting on a pre-stretched soft elastic layer glued onto a rigid substrate. Our study shows that the capping film is always unstable for nonvanishing applied voltage. The undulation wavelength of the film is initially quite large, but undergoes a sharp transition when the voltage is increased to a critical value. In this case, well aligned winkles with considerably smaller wavelength appear in the fashion parallel to the tensile direction of the soft elastic layer. The magnitude of the wavelength is tunable, thus providing a mechanism to control the wrinkling pattern of the capping film. (C) 2010 Elsevier B.V. All rights reserved.