A fast curing, coating composition that is adapted for use as an a auotmotive topcoat and which upon curing forms a hard, glossy, durable coating exhibiting excellent resistance to solvents and water. The coating composition which may contain greater than about 55 percent by weight of nonvolatile solids and, exclusive of pigments, solvents and other nonreactive components, consists essentially of:(A) a bifunctional copolymer bearing hydroxy functionality and pendent epoxy functionality, having a number average molecular weight (M.sub.n) of between about 1500 and about 10,000 and a glass transition temperature (Tg of between about -25.degree. and about 70.degree.;(B) a reactive catalyst comprising at least one phosphonic acid derivative;(C) an amine-aldehyde resin crosslinking agent; and(D) optionally, a hydroxy functional additive.The phosphonic acid derivative catalyst is included in the composition in an amount sufficient to provide between about 0.8 and about 1.4 equivalents of acid functionality in copolymer (A), and the amine-aldehye resin crosslinking agent is included in the composition in an amount sufficient to provide at least about 0.4 equivalents of nitrogen crosslinking functionality for each equivalent of hydroxy functionality included in the composition.