An embedded cluster model, employing a point charge field to correctly account for the electrostatic effect of the surrounding lattice, is used to study the adsorption of water and methanol at zeolite Bronsted acid sites. The effects of both the point charge field and electron correlation (studied at the second order Moller-Plesset (MP2) and density functional theory (DFT) levels) are reflected in the predicted substrate structures, binding energies and H-1 NMR shifts. Both result in enhanced substrate binding to yield good agreement with experiment, and an increased degree of proton transfer to the substrate, an effect particularly evident in the case of methanol. There is a suggestion from a comparison with measured H-1 NMR shifts that this effect is somewhat overestimated by the model used here.