The effects of co-feeding excess hydrogen on the propane aromatization reaction over Ga2O3, H-ZSM-5 and physical mixtures of Ga2O3/H-ZSM-5 are described and discussed. For Ga2O3 alone co-feeding excess hydrogen gives a significant increase in the conversion and aromatic selectivity. For H-ZSM-5 alone co-feeding excess hydrogen gives a slight decrease in conversion and increases the selectivity to hydrogenated products. For Ga2O3/H-ZSM-5 physical mixtures co-feeding excess hydrogen leads to a significant decrease in the conversion and aromatic selectivity. We propose that hydrogen can be used as a reactive probe molecule for this reaction. Experiments are also described for propane aromatization over physical mixtures of powdered Ga2O3 and pelleted H-ZSM-5 that provide evidence for the reversible formation of the active site for this reaction.