We report improvement in crystalline quality of In0.52Al0.48As∕In0.53Ga0.47As multiquantum wells (MQWs) and compositionally graded InAlAs∕InAlGaAs metamorphic buffer grown on GaAs by using postgrowth rapid thermal annealing (RTA). Dependence of optical and structural properties of the MQWs on RTA was investigated by using photoluminescence (PL) and triple-axis x-ray diffraction measurements. After the RTA, the PL intensity of the MQWs increased, while the linewidth decreased. Also, the triple-axis contour maps of the MQWs showed increase in peak intensity of epilayers as well as crystalline reformation indicated by narrower mosaic spread and restoration of epilayer tilt to the substrate orientation.