The growth of InAsN/InGaAs(P) quantum wells (QWs) on InP substrates by gas-source molecular-beam epitaxy and a rf plasma nitrogen source is reported for the first time. The double crystal x-ray diffraction satellite peaks of the InAsN/InGaAsP multiple quantum well (MQW) samples are sharper than those of the pure InAs/InGaAsP MQW samples, showing that a flatter heterointerface is achieved due to the smaller lattice mismatch. However, broadening of the satellite peaks and degradation of the photoluminescence (PL) intensity due to the increase of the nitrogen composition in these InAsN/InGaAsP MQWs suggest the existence of defects introduced by the small diameter nitrogen atoms located on arsenic sites. The PL result also shows that the peak energy decreases as the nitrogen composition increases. The estimated transition energy shrinkage coefficient is -31 meV/at.% nitrogen. The largest nitrogen composition obtained in this study is 5.9%, and its 10 K PL peak wavelength is similar to2.6 mum (480 meV). The effects of growth temperature on nitrogen composition and PL intensity are also discussed.