Near normal-incidence spectral reflectance has been used to monitor the growth of AlAs, GaAs, and AlGaAs thin films by MOCVD in real time. The method has been used in a research rotating disk CVD reactor and in a modified commercial horizontal channel reactor. Reflectance is simple, robust, and is insensitive to perturbations such as mechanical strains, wafer rotation, and imperfect windows commonly encountered in an actual MOCVD system. Data may be collected over a wide spectral range, 390 to 950 nm, in less than one second using a multichannel detector and broad-band light source. This wide bandwidth provides detailed compositional discrimination and greater thickness sensitivity than single-wavelength measurements. The technique may be used to extract wavelength-dependent optical constant data under growth temperature conditions. Examples from the growth of multi-layered structures used in the fabrication of Vertical Cavity Surface Emitting Lasers is presented. The method shows promise as a valuable tool in process modeling, optimization, and control.