We report quantitative agreement between Monte Carlo simulation and the experimental NMR chemical shift of Xe-129 adsorbed in the supercages of zeolite Y. This agreement supports previous assertions, originating from Ripmeester and Fraissard, that the Xe shift can in principle provide a sensitive measure of the structure imposed on Xe by the three-dimensional potential field provided by the crystal structure of the zeolite. Up to a loading of 7 Xe/cage at 300 K, we verify that the linear rise of shift with loading is due solely to Xe-Xe interaction. We also find excellent agreement at 144 K between simulation and the nonlinear experimental data of Cheung et al. The nonlinear dependence of shift on loading arises both from repulsive Xe-Xe and from repulsive Xe-O interactions. Finally we verify that the effect of temperature on the shift at zero loading can be related to the change of Xe-O pair correlation function at short separations.