The adsorption of methanol on cluster models of Bronsted acid sites of zeolite catalysts has been investigated by ab initio quantum chemical methods at the Hartree-Fock self-consistent, field (SCF) and at the second-order Moller-Plesset perturbation theory (MP2) levels. Among the two possible structures of the adsorption complex, the neutral methanol H-bonded to the zeolite OH group and the methoxonium cation attached to the zeolite surface (ion-pair), only the former is a minimum. The ion-pair structure is a transition structure for the proton transfer from one lattice oxygen to a neighboring one via the adsorbed methanol. However, the energy difference between both structures is only a few kJ/mol. There is a broad and shallow potential well which accommodates two symmetry-equivalent neutral complexes with the Bronsted proton attached to different O-sites of the lattice and the ion-pair structure connecting them. For the complex of methanol with the largest zeolite model optimized at the MP2 level, H-1 NMR chemical shifts of 10.8 and 17.4 ppm are predicted for the neutral and the ion-pair structure, respectively. The former value agrees well with the observed shift and therefore explains the observed signal as caused by fast exchange of the zeolite and methanol hydroxyl protons of the neutral structure.