Raman light scattering experiments in lattice‐matched InGaAsP/InP multiple quantum wells are reported. Use of laser light below the InP band gap permitted study of right‐angle scattering with the scattered light emerging parallel to the layers. Scattering by the binary InP longitudinal optic (LO) and transverse optic (TO) phonons dominated the spectra. The polarization selection rules for the TO and LO scattering were found to differ strongly compared to those operative in bulk InP. This is interpreted as arising from the interchange of the LO and TO phonon frequencies as expected in a dielectric continuum slab whose thickness is small compared to the wavelength of the incident radiation. In addition weak Raman scattering by a mixture of InGaAs and InP vibrations in the quaternary well material is reported.