We demonstrate a tunable nanosecond optical parametric oscillator with a narrowed signal spectrum. This was done by use of a volume Bragg grating based retroreflector, which makes the tuning simple and yields a compact design. Using periodically poled ${\mathrm{KTiOPO}}_4$ as the nonlinear medium, we generated $0.42\mathrm{mJ}$ of signal energy at $760\mathrm{nm}$ with a tuning range of $5\mathrm{nm}$ $\left(2.6\mathrm{THz}\right)$ and a bandwidth of $0.25\mathrm{nm}$ $\left(130\mathrm{GHz}\right)$ when the oscillator was pumped at $532\mathrm{nm}$ with $1.3\mathrm{mJ}$ of energy.