Stable index‐guided operation of variable stripe strained‐layer InGaAs‐GaAs‐AlGaAs lasers achieved by MeV oxygen implantation‐induced disorder of the active region is demonstrated. Well‐behaved near‐ and far‐field patterns for lasers implanted with 5×1016cm−2and 1×1017cm−2oxygen are observed to be stable with increasing drive current. Comparison with unimplanted, oxide‐defined stripe lasers fabricated from the same wafer indicates a dramatic improvement in emission characteristics as a result of the presence of a lateral real‐index waveguide in the oxygen‐disordered regions which is stronger than the carrier‐induced antiguide present in unimplanted InGaAs‐GaAs strained‐layer lasers.