The effect of repetitive rapid thermal annealing (RTA) at 800°C was investigated in the strained-layer superlattices (SLS's) In.2Ga.8As/GaAs (80Å/80Å) and In.3Ga.7As/GaAs (80Å/80Å) using photoluminescence (PL) and the highly sensitive absorption technique photothermal deflection spectroscopy (PDS) . The samples were repetitively annealed at 800 °C for 15 seconds intervals up to a total time of 45 seconds. Between each anneal, PL spectra were taken at 1.4 K. PL measurements show initial red shifts and subsequent blue shifts with increased annealing times. These shifts were accompanied by a decrease in the intensity of the PL peaks. PDS absorption data were measured at room temperature for the as-grown materials and for the 45 seconds RTA. The PDS data measured at room temperature for 0 and 45 seconds RTA were consistent with the PL data. The spectral shifts may indicate a competition between the effects of thermally driven strain relaxation and chemical interdiffusion.