In this work, a transparent dielectric elastomer actuator is integrated into a tunable transmission grating. A 13 micron-thick silicone membrane has been sandwiched between two 750 nanometer-thick transparent ionogel electrodes to fabricate a transparent dielectric elastomer actuator. By structuring the top transparent ionogel electrode into a sinusoid grating profile, with 2 µm period, the transparent dielectric elastomer actuator is transformed into a tunable transmission grating. The structured stretchable electrode plays both the role of electrical conductor and optical grating. When 1300V is applied between the two stretchable ionogel electrodes, the actuator presents a linear strain of 12.8 percent, which correspond to a 1.4 degree change in the first diffraction angle for green light. The transparent ionogel electrode also present the self-clearing property, thus further extending the lifetime of the actuator at high drive voltages. The ionogel electrodes maintain the accurate grating shape for several weeks, and could be patterned into the shape of any diffractive element.