This article reports on the growth of GaInAsP/InP by solid source molecular beam epitaxy the incorporation efficiencies of the group V dimer and tetramer molecular species, and the functioning of the MBE system. The incorporation efficiency of As-4 is found to be close to that of As-2 while the incorporation efficiency of P-4 is only half that of P-2. Room temperature and low temperature photoluminescence measurements demonstrate that material grown using AS(4) is Of better quality than that grown using As-2. After the use of P-4, a tenfold increase in the pressure burst occurs upon warming of the liquid nitrogen shrouds, and is believed to be caused by the formation of deposits containing white phosphorus. The atomic As to P incorporation ratio is approximately 10, when using P-2, and exhibits a substrate temperature dependence.