Abstract: A molding composition and method for the preparation of same wherein the molding composition is formulated of an unsaturated thermosetting prepolymer, a thermoplastic polymer prepared by interpolymerization of (1) a polymerizable ethylenic monomer, (2) an organic acid or anhydride containing at least one carboxyl group and one double bond per molecule, (3) an unsaturated elastomer having an average molecular weight less than 40,000 and (4) an unsaturated elastomer having an average molecular weight greater than 43,000, an unsaturated cross-linking agent which is capable of serving as a solvent for the prepolymer and the thermoplastic polymer and a non-reactive solvent. The combination of the thermoplastic polymer and the non-reactive solvent are believed to act together to reduce the amount of shrinkage of the thermosetting prepolymer when the latter is cured with the cross-linking agent.