The unique properties of dilute nitrides, such as GaPN(As), make them highly promising for use in solar cells and optoelectronic devices. In this work we report on the investigation of the effects of rapid thermal annealing on the structural and optical properties of GaPN(As) solid solutions. The GaPN(As)-based heterostructures were grown on a silicon substrates by plasma assisted molecular beam epitaxy. The effect of rapid thermal annealing on the properties of these materials was studied using photoluminescence spectroscopy and X-ray diffraction analysis.