Densities, refractive indices, and speeds of sound at 298.15 K, and isobaric vapor-liquid equilibria data at 101.3 kPa were reported for binary mixtures containing methanol + ethyl propionate and vinyl acetate + ethyl propionate. Excess molar volumes, refractive index deviations, and changes of speed of sound on mixing were calculated from the measured results and fitted to Redlich-Kister polynomials. VLE experimental data were tested for thermodynamic consistency by means of a modified Dechema test and were demonstrated to be consistent. The activity coefficients were correlated with the Margules, van Laar, UNIQUAC, NRTL, and Wilson equations with two suffixes and the Wilson model with three suffix equations. The ASOG model also was used for prediction. The methanol (1) + ethyl propionate (2) system shows an azeotrope at x(1) = 0.984.