We report on a new method for the generation of phosphorus beams in molecular beam epitaxy: the use of a valved, solid cracker source. The valved solid source avoids previous difficulties associated with the use of solid phosphorus, and provides an attractive alternative to the use of phosphine. The use of red phosphorus does not interfere with the subsequent growth of high quality arsenides in the same growth chamber. The performance of this valved phosphorus source is illustrated by the growth of two ternary phosphides, Ga0.5In0.5P and Al0.5In0.5P. The quality of the phosphides reported here is comparable to the best results reported by other growth techniques. The effects of composition, growth temperature, and P2flux on the films’ characteristics are reported. Indium desorption during growth is found to be substantially greater in AlInP than in GaInP.