We report the growth and characterization of 1.55 mu m wavelength GaInAsP based semiconductor lasers grown by solid source molecular beam epitaxy. Quaternary compositions were reproducible over time. Photoluminescence and x-ray diffraction spectra indicate abrupt quantum well interfaces. Separate confinement heterostructure laser diodes with four quantum wells had threshold current densities as low as 580 A/cm(2) and 275 A/cm(2) for unstrained Ga0.47In0.53As and strained Ga0.27In0.73As0.8P0.2 wells, respectively. These results are as good as the best results reported for similar lasers grown by any growth technique.