We present experimental results of field‐enhanced photorefractive two‐beam coupling and gain in Cr‐doped strontium barium niobate crystals and its dependence on dopant concentrations. Increases in the exponential gain factor by more than a factor of 2 were observed by applying a field of up to 10 kV/cm. This property has potential applications such as switchable optical phase conjugators, limiters, and thresholding devices.