We report strong band gap photoluminescence at room temperature in dilute quaternary GaNxAs1-x-yBiy alloys (x < 1.6%,y < 2.6%) grown by molecular beam epitaxy. The band gap of the alloy can be approximated by the band gap of GaAs minus the reduction in gap associated with the effects of N and Bi alloying individually. A one-parameter method for fitting the composition dependence of the band gaps of dilute quaternary semiconductor alloys is proposed which is in excellent agreement with data for Ga1-yInyNxAs1-x. (C) 2005 American Institute of Physics.