We report ab initio quantum-chemical calculations at the level of second-order many-body perturbation theory aimed at the equilibrium between the all-trans (ttt) and the trans-gauche-trans (tgt) conformations of dimethoxyethane, which is the smallest analog of poly(ethylene oxide). Solvent effects are accounted for by two continuum models : one assumes statistically fluctuating electric fields around the dimethoxyethane molecule caused by the solvent, and the other is an Onsager reaction-field model. We find the ttt conformer to be more stable in the gas phase. Use of the stochastic field model has no effect on the relative stabilities, whereas the reaction-field method brings the energy of the tgt conformer down very dose to the ttt energy. We conclude that the gauche effect in dimethoxyethane and, by analogy poly(ethylene oxide), is mainly due to the presence of a polarizable environment and not to some intrinsic conformational preference.