The activation of a dimethylgallium/ZSM-5 precursor to well-defined reduced and oxidized species is studied by in situ Ga K edge XANES. The precursor is prepared by chemical implanting of trimethylgallium on acidic HZSM-5. Subsequent reduction leads to charge-compensating Ga+ species. Direct oxidation of the trimethylgallium precursor leads to various forms of gallium oxide and regeneration of Bronsted acid protons. Oxidation of the reduced Ga+ species yields predominantly to GaO+ species. The GaO+ species exhibit a much higher H-2/D-2 exchange activity than reduced Ga+ species.