Growth studies of Ga1-xInxAs1-yNy quantum wells with indium contents covering the full compositional range (x(In)= 0 ... 1) have been performed using a gas-source MBE and a valved nitrogen plasma source manufactured by the company ADDON. By using GaAs- and InP- as well as InAs substrates, differently strained GaInAsN-layers were produced, offering a complete overview of the relative bandgap shrinkage with respect to nitrogen-free GaInAs structures, after 1 % nitrogen is incorporated. We have shown that this relative bandgap shrinkage depends on the absolute value of indium content of the GaInAs host matrix. As a result a new parameter E was defined describing the relative bandgap shrinkage per percent incorporated nitrogen. When plotting this parameter over the complete range of indium content, a nearly linear decrease occurs. (C) 2008 Elsevier B.V. All rights reserved.