In the present work a group contribution-associating-equation of state (GCA-EOS) is developed for the modeling of phase equilibria found in the near critical fluid extraction and dehydration of oxygenated compounds from aqueous solutions. The new equation of state is obtained by the inclusion of a ’group’ contribution associating term to the GC-EOS model. The definition of a unique hydroxyl group to represent the association effect of hydrogen bonding in water and alcohols, greatly simplifies the extension of the model to multicomponent mixtures. This approach has been applied to determine the parameters for a common hydroxyl group for water, primary and secondary alcohols. On this basis, revised group and binary interaction dispersive parameters for water, primary and secondary alcohols, alkane groups, light hydrocarbons and CO2 have been determined. Model predictions for binary and ternary data are presented.