Co-solvency is a phenomenon where a small quantity of co-solvent is added to a bulk solvent to enhance the solubility of a desired solute in the mixture. Correspondingly, there is a second effect, co-nonsolvency, where a solute of interest, 2-(methacryloyloxy)ethylphosphorylcholine) (MPC) in this study, is soluble in either of the pure solvents used in a co-solvent mixture, but not in a mixture of specific compositional ratio. Despite much interest in these phenomena, there is currently little structural understanding of the in-solution molecular correlations that drives them. Here we propose to use H/D isotopic substitution neutron scattering methods to investigate the solution structure of ethanol-water-MPC at co-solvency/co-nonsolvency compositions to provide a baseline model of common media in which the effects take place.