Experiments in which bulk MoO3 has been diluted in silica or alumina reveal a "corrected" TPR pattern in which the bulk oxide reduces at the same temperature as the supported crystalline phase. The reduction patterns for diluted bulk MoO3, in conjunction with an XRD study of the reduction process and a recent comprehensive speciation theory have greatly assisted the assignment of peaks for silica and alumina supported samples. A simple interpretation of TPR patterns has been applied with good agreement to the body of MoO3 TPR literature. With consistent interpretation, temperature programmed reduction might be employed with increased confidence to characterize supported MoO3 and perhaps other supported oxides.