Employing molecular beam depletion spectroscopy and Fourier transform infrared matrix spectroscopy, respectively, we have studied the O-H stretching vibrations of the glycine conformers I, II, and III. The glycine molecules were either deposited into large liquid helium clusters He-N, (N) over bar=11000, T-He=0.4 K) or trapped in various rare gas matrices (Ne, Ar, Kr) at temperatures below 12 K. By extrapolating the experimental data plotted as a function of the square root of the critical temperature of the matrix material, the positions of the gas phase absorption bands were estimated to be 3585 +/- 2 cm(-1) (conformer I), 3295 +/- 3 cm(-1) (conformer II), and 3580 +/- 5 cm(-1) (conformer III). The experimental results are compared with recent ab initio calculations.