Collisional removal of the v'=0 level of the A (2)Sigma (+) state of the OH radical has been studied as a function of rotational level N' at room temperature. OH in high rotational levels of the X (2)Pi (i) state were created by 193 nm photolysis of HNO3 and excited to A (2)Sigma (+) by a tunable dye laser. Time decays of fluorescence at varying pressures were measured. For O-2 and H-2, the quenching cross section sigma (Q) decreased with increasing N' until N'similar to 10; for higher N' it appears to remain approximately constant. Xe behaves the same way except that the decrease continues to N'=15. For Kr, sigma (Q) appears to decrease to within experimental error of zero at N'=10; and for N-2 it was within error of zero above N'=10. These results have implications for laser-induced fluorescence atmospheric monitoring of OH and combustion temperature determinations, as well as a fundamental understanding of collisional quenching. Quenching of OH, N'similar to1, by HNO3 was found to be 81 +/-8 Angstrom (2).