A pulsed injection-seeded optical parametric oscillator (OPO) has been studied and its suitability for applications requiring dual-wavelength operation has been demonstrated. Single-mode operation was achieved by injection seeding the OPO with radiation from a tunable diode laser. The OPO was tuned over a range of 90 nm (1490.6–1580.3 nm) with an average output energy of 5 mJ (7% conversion efficiency) and a linewidth of 140 MHz. The inherent stability of the travelling-wave cavity design has enabled stable operation to be achieved without active stabilisation of the cavity. Dual-wavelength operation has been achieved by injecting two seed frequencies simultaneously. The suitability of the OPO for infrared Differential Absorption Lidar (DIAL) measurements has been demonstrated by making a range-resolved measurement of atmospheric methane.