Comprehensive characterization of epitaxial growth by metal organic vapor phase epitaxy (MOVPE) requires a combination of thin-film, near-surface-, and surface-sensitive techniques to determine layer thicknesses and compositions, composition of the most recently deposited material, and surface chemistry, respectively. These data can be obtained non-destructively by spectroscopic ellipsometry (SE) and reflectance-difference (-anisotropy) spectroscopy (RDS/RAS). Here we describe the first unified optical system, basically a rotating-polarizer ellipsometer (RPE) integrated into a modified commercial rotating-sample MOVPE reactor, that performs both SE and RDS simultaneously with a single optical path. Data are obtained in parallel from 240 to 840 nm with a high-speed 16-bit photodiode array (PDA) at a repetition rate greater than 2 Hz and a precision of +/-0.0001. We provide examples of its use, and show in particular that Cap intermixes with Si during the initial stages of heteroepitaxy. Capabilities of the presented configuration and its potential for future investigations are discussed.