We report measurements of total flux for six circumstellar SiO maser sources. Both polarizations were measured simultaneously for these highly polarized sources. We compare SiO curves with the infrared flux, especially the infrared minima, which are observed to coincide in phase with the optical minima. The comparisons of SiO and infrared flux at light minimum are the most straightforward and indicate a characteristic phase lag for several of our sources. When interpreted in terms of observed physical motions associated with these stars, the SiO-infrared phase lag of 63-129 days can be used to infer a scale size on the order of 1013 cm. The corresponding light-travel time is of the order of 1017 cm, which is well outside the SiO line formation region.