We present an electrically actuated tunable optical grating based on dielectric elastomer actuators. A simple fabrication protocol is presented, which integrates the grating with the actuating mechanism both made of soft elastomers, improving the tunability of the grating. The device is designed to be operated in the transmission mode. It exhibits a continuous period tunability of 34.4% at an actuation voltage of 5.5 kV, which is an improvement over reported tunable optical gratings.