Abstract: Hydroxy functional polyester graft copolymers are provided. The copolymer is crosslinkable by hydroxy-reactive crosslinking agent and, in particular, is suitable for use in thermosetting coating compositions adapted to form a flexible cured coating over a variety of substrates, such as metal and plastic. The copolymer has a number average molecular weight between about 1300 and about 15,000, has a hydroxyl number between about 30 and about 300, and is the reaction product of carbon-carbon double bond-reactive monoethylenically unsaturated monomer with hydroxy functional carbon-carbon double bond-bearing branched polyester macromer. The macromer is the reaction product of (i) hydroxy functional polyester reactant containing 0-10 urethane linkages per molecule with (ii) silane compound having the general chemical formula: ##STR1## wherein X is an organic group or (--Si--O--).sub.