We report gas-source molecular beam epitaxy of high-quality Ga1-xInxNyP1-y/GaAs heterostructures grown on a GaAs (100) substrate. Bulk Ga1-xInxNyP1-y, as well as Ga1-xInxNyP1-y/GaAs, quantum well (QW) samples were grown and characterized by a high-resolution x-ray rocking curve and photoluminescence (PL). With nitrogen incorporation, the PL peak redshifts, indicating band gap reduction. Rapid thermal annealing for 10 s in a 100% N-2 ambient with 700 degreesC temperature improves the Ga0.46In0.54N0.005P0.995PL intensity by a factor of 10 and reduces the linewidth to two fifths. We use both bulk and QW PL experimental data to determine band lineup for Ga1-xInxNyP1-y/GaAs heterostructure. Most of the band reduction is attributed from the conduction band with nitrogen incorporation.