A single-mode cw optical parametric oscillator (OPO) based on a bulk Bragg grating is reported. The OPO is capable of producing multiwatt output power both at the signal (1535 nm) and idler (3468 nm) wavelengths with a side-mode suppression ratio better than 29 dB. Coarse frequency tuning of 120 GHz(4 cm(-1)) and fast mode-hop-free tuning of 40 GHz(1.3 cm(-1)) have been achieved by scanning the grating temperature and the OPO pump laser, respectively.