A molding composition containing a graft polymer is disclosed. The graft is a product of a free-radical emulsion polymerization of resin-forming vinyl monomers in the presence of rubber present in latex form having a glass transition temperature of ≦0° C. using an initiator combination comprising a persulfate compound and a redox initiator system. The process for preparing the graft polymer entails adding the persulfate compound at the beginning of the graft polymerization reaction and a later addition of the redox initiator. The composition that features good gloss and flowability is suitable for the preparation of molded articles.