The detailed characterization of epitaxial growth by metal organic vapor phase epitaxy (MOVPE) and its closed-loop feedback control at the sample level require a combination of thin-film, near-surface, and surface-sensitive techniques to determine layer thicknesses and compositions, the composition of the most recently deposited material, and surface chemistry, respectively. These data can be obtained nondestructively by spectroscopic ellipsometry (SE) and reflectance-difference (-anisotropy) spectroscopy (RDS/RAS). We describe the first unified optical system, basically a rotating-polarizer ellipsometer (RPE) integrated within a modified commercial rotating-sample MOVPE reactor, that performs both SE and RDS simultaneously in a single optical path. We provide examples of its use, showing in particular that GaP can intermix with Si during the initial stages of heteroepitaxy, and demonstrating sample-driven closed-loop feedback control of epitaxy through the fully automatic deposition of an InxGa1—xP parabolic quantum well. These results illustrate capabilities of the presented configuration and its potential for future use.