BInGaN quaternary alloys with up to 2% boron and 14% of indium have been grown on GaN/sapphire template substrates by metal-organic vapour phase epitaxy (MOVPE). Epitaxial layer composition was determined by secondary ion mass spectroscopy (SIMS), and confirmed by X-ray photoelectron spectroscopy (XPS). Bandgap energies were measured using optical transmission and reflection spectroscopy. We find that boron incorporation in BInGaN reduces the bandgap, causing an effect similar to the increase of indium content in InGaN. However, adding boron has the advantage of decreasing the lattice mismatch with conventional GaN substrates.