Low-temperature transmittance and room-temperature photoreflectance spectra are presented for a series of InxGa1-xAs1-yNy/GaAs (x approximate to 15%) strained-layer multiple quantum well structures grown by molecular-beam epitaxy with a nitrogen concentration ranging from 0% to 1.7%. Nitrogen incorporation causes an increase of the conduction band offset and effective mass. Moreover, the variation of the valence band alignment can be explained by the lowered compressive strain in the wells; the unstrained valence band offset remains constant, Results are described using the formalism of the band anticrossing model.