Under certain growth conditions, the single‐crystal alloy Ga0.5In0.5P spontaneously orders on the group III sublattice with gallium and indium atoms occupying alternating (111) planes. The ordered structure has been associated with variations in the observed band gap, extra and moving optical transitions, anomalous polarization effects, and very long low‐temperature photoluminescence lifetimes. The observed variations may be attributed to ordering or potential fluctuations associated with imperfect and nonuniform ordering and are a complex function of the growth parameters. Such anomalous optical properties may also be observed in other alloys that exhibit potential fluctuations, e.g., amorphous silicon and CuInSe2.