The ionization processes of the Ar_M, Xe_N and Xe_NAr_M clusters in a supersonic beam with multiphoton excitation were studied. The third 263 nm harmonics of a femtosecond Ti : sapphire laser were used for excitation and ionization. Kinetic energy spectra of photoelectrons has been recorded by a magnetic bottle time-of-flight electron spectrometer. Analysis of the electronic spectra of multiphoton ionization of clusters shows that, in heteronuclear clusters, the transfer of excitation energy between xenon and argon atoms plays a significant role in ionization.