The optical parametric oscillator (OPO) is a simple and effective method to generate desirable and specific wavelength. The OPO laser is small, portable and has high efficiency, low threshold and can be operated at room temperature. In this paper, we report an electrically controlled tunable optical parametric oscillator operating from wavelength of 2.97 to 6.35 μm. The nanosecond OPO is based on BaGa4Se7 crystal and pumped by a 10 ns 1.06 μm electro-optic Q-switched Nd:YAG laser. The output mid-infrared idler wave can be tuned from 2.97 μm to 6.35 μm with pulse energy as high as 1.97 mJ at 3.8 μm and can be even increased with more pump power. The central idler wavelength is 4.66 μm (rotation angle is 0°). The output idler wavelength can be tuned by turning the rotation angle of the crystal, which is controlled by an electronic motor. The motorized continuous rotation stage is compact and highly precise with minimum rotation step of 0.002 5°. This enables the fine tuning of the phase-matching angel and the resulting output wavelength.