Growth of GaxIn1−xAsyP1−y was performed on (001) InP by molecular‐beam epitaxy employing solid phosphorus and arsenic valved sources. Relative anion incorporation rates were found strongly dependent upon the Ga mole fraction, growth temperature, and incident As and P beam fluxes. The relative incorporation of As and P can be predicted from the ratio of the square of the incident column‐V fluxes. Although the As anion always incorporated preferentially into the lattice, significant enhancement in P incorporation was observed as growth temperature and Ga mole fraction increased. Strong spinoidal decomposition and a temperature‐dependent surface morphology was found for lattice‐matched compositions having peak photoluminescence emission wavelengths between 1.25 and 1.36 μm. Heterojunction laser diodes utilizing different GaxIn1−xAsyP1−y active regions were fabricated with emission ranging from 1.21 to 1.53 μm. The best broad area threshold current density obtained for a 500 μm cavity length was 1.7 kA/cm2 with a maximum two facet slope efficiency of 0.24 W/A, which is comparable to the state‐of‐art performance.