The intensity ratio of the neutral oxygen "red" emission lines O(D-1(2)-P-3(2,1))630.0 nm to 636.4 nm has been measured in terrestrial nightglow spectra obtained from astronomical instrumentation. The observed intensity ratio, I( 630.0 nm)/I(636.4 nm)) 2.997 +/- 0.016, is consistent with the value of 2.997 determined from the recent spontaneous emission coefficient calculations of Storey and Zeippen ( 2000), distinctly lower than the value of 3.10 calculated from those coefficients recommended by the National Institutes of Standards and Technology (NIST), and lower than the value of 3.1 measured by laboratory experiment (Kernahan and Pang, 1975). A weak emission line measured at 639.174 +/- 0.003 nm has also been observed in these spectra and identified as the highly optically forbidden transition O(D-1(2)- P-3(0)) 639.1773 nm of the same multiplet as the red lines. The observed intensity ratio, I( 636.4 nm)/I(639.2 nm)) 1700 +/- 700, is a factor of 2 lower than that predicted by most recent theoretical calculations.