Data are presented showing that high quality visible‐spectrum multiple‐ quantum‐well In1−x′Gax′P1−z′Asz′‐ In1−xGaxP1−zAsz(x≳x′,z≳z′) heterostructures can be grown on GaAs1−yPy(y∼0.30) substrates by a mechanized computer‐controlled liquid phase epitaxial process. Undoped visible‐spectrum (6600–6000 A˚) heterostructures with as many as 12 uniform coupled quantum wells (Lz∼160 A˚) have been grown and have been examined (77 and 300 K) via photopumping. Phonon participation in the recombination process is dominant in these quaternary quantum‐well heterostructures and lowers the recombination energy by as much as 2?&ohgr;LO(InGaPAs)∼68 meV below the lowest (n=1,n′=1′) confined‐particle transitions.