Optical second harmonic generation (SHG) and nonlinear magneto-optical Kerr effect (NOMOKE) are experimentally studied in Co x Ag 1− x and (CoFe) x (Al 2O 3) 1− x granular films which exhibit giant magnetoresistance (GMR) effect. Nonmonotonous dependences of the magnetoresistance, SHG intensity and NOMOKE magnetic contrast on volume fraction of the magnetic component x are found. The maximum of the NOMOKE magnetic contrast is attained at the value of x close to that providing the maximum of the magnetoresistance. The resonances observed in the SHG spectra are associated with the local surface plasmon modes at the granule/host interfaces.