High-resolution electron microscopy has been used to characterize the microstructure of thin Co/Cu metallic multilayers grown on Si(100) substrates by dc magnetron sputtering. The nature of the buffer layer between the silicon wafer and the multilayer had a significant effect on the structural integrity of the multilayer. An increase in grain size was observed as a function of Cu layer thickness, with grain sizes typically being at least 3-4 times the bilayer period. A high degree of structural ordering was observed in superlattices comprised of thicker Cu layer with large grains often spanning the complete multilayer stack. Complementary magnetic measurements enabled the microstructure to be related to the oscillatory exchange coupling and large magnetoresistance exhibited by these thin magnetic films.