Vulcanizable elastomeric compositions are described which comprise an elastomer and from about 0.001 to about 0.1 lb mole of metal per 100 lbs of elastomer, the metal content comprising a mixture of copper and zinc, said metals being present as(a) an organic carboxylic acid salt consisting of copper and zinc combined with one or more carboxylic acids,(b) a combination of two or more copper and zinc salts of organic carboxylic acids, or(c) a combination of a metal salt of an organic carboxylic acid and a mixed organic acid salt complex.Such vulcanizable elastomeric compositions exhibit improved adhesion to brass plated metal surfaces and are, therefore, useful in preparing rubber laminates containing metal reinforcing elements.