Experimental vapor-liquid-liquid equilibrium (VLLE) compositions have been measured, in an equilibrium cell, for the four-component system methane + n-octane + monoethylene glycol (MEG) + water at pressures from (3.1 to 15.0) MPa and temperatures from (281 to 363) K. A total of 27 sets of equilibrium data have been obtained using three different types of feed mixture. The relative volumes of the three phases have also been obtained for each equilibrium data set. The measurements illustrate the pressure and temperature dependence of the dehydrating effect of MEG in the vapor phase and also show that the solubility of the hydrocarbons in the aqueous phase is considerably enhanced by the presence of MEG. Some implications for the design of gas dehydration plants have been briefly discussed.