[en] Preliminary results are presented of a program to study the optical and infrared continuum emission of quiescent QSOs using simultaneous UBVRIJHK photometry. The amplitude of variability in six of the seven sources discussed is greatest in the blue and ultraviolet and decreases toward longer wavelengths. Only 3C 273 exhibits variability at all wavelengths observed, changing by a similar amount in each spectral band.All of the other QSOs were nonvarying at 2.2 microns, despite variations in the visible and ultraviolet. This variability behavior and the optical-infrared spectral energy distribution in each object except 3C 273 strongly suggest that the infrared and variable optical continuum emission arise from distinct sources within the QSOs. Several possible models of the origin of the continua are examined. 29 references