Femtosecond pump-probe spectroscopic studies on mixed methanol/water clusters are presented. Two-photon absorption of light was employed to generate methanol molecules in the 3p Rydberg excited state, with transfer to the 3s Rydberg state during the ensuing dynamics. The experiments provide evidence that excited state hydrogen transfer occurs between a methanol molecule, which undergoes hydroxyl dissociation following electronic excitation, and a water molecule, leading to the involvement of a metastable H3O species.