Rapid thermal annealing (RTA) of 1000Å GaNAs films grown on (100) oriented GaAs substrate by radio frequency (RF) plasma assisted solid-source molecular beam epitaxy was studied by low-temperature photoluminescence (PL) and high-resolution x-ray diffraction (HRXRD). Samples with nitrogen content of 13 and 2.2% have shown an overall blueshift in energy of 67.7meV and an intermediate redshift of 42.2meV in the PL spectra when subjected to RTA at 525–850°C for 10min. It is also shown that the sample, which is annealed at temperature range of 700–750°C, has the highest photoluminescence efficiency (1.7–2.1 times increase in integrated PL intensity as compared to the as-grown sample). Reciprocal space mapping of the as-grown GaNAs samples obtained by using triple-crystal HRXRD shows the presence of interstitially incorporated of N atoms with no lattice relaxation in the direction parallel to the growth surface. These results have significant implication on the growth and post-growth treatment of nitride compound semiconductor materials for high performance optoelectronics devices.