This letter reports exceptionally broadband tuning of a continuous-wave optical parametric oscillator (cw OPO) using a temperature tuned, nonlinear crystal of MgO:LiNbO3 pumped by a diode-pumped, intracavity doubled Nd:YAG laser. The tuning range from 788 to 1640 nm, is about four times broader than those ever reported in cw OPOs operating around 1 μm. This performance was accomplished by newly developed, extremely broadband, high-reflection mirrors for the doubly resonant oscillation, designed to have a reflectivity of 99% from 0.7 to 1.6 μm. Threshold pump power increased from 80 mW near degeneracy to 150 mW at the tuning band edge in a double pass pumping configuration. © 1998 American Institute of Physics.