Accurate QED evaluations of the one- and two-photon interelectron interaction for the configurations 1s(1/2)2s(1/2) S-1(0) and 1s(1/2)2s(1/2) S-3(1) in He-like ions and for the configurations (1s)(2)2s(1/2) and (1s)(2)2p(1/2) in Li-like ions with nuclear charge numbers 30 less than or equal toZ less than or equal to 92 are performed. The three-photon interaction is also partly taken into account. The QED theory of these corrections is provided by the adiabatic S matrix and by the line-profile approach. The Coulomb gauge is employed. The results are compared with available experimental data and with different calculations.