We present results on n-channel inversion-type indium phosphide (InP) metal-oxide-semiconductor field-effect transistors (MOSFETs) with atomic layer deposited (ALD) beryllium oxide (BeO) gate dielectric using the gate-last process. InP MOSFETs with the BeO gate stack were realized with high performance including the improved drive current, subthreshold swing, and a peak effective electron mobility. The transmission electron microscopy and x-ray photoemission spectroscopy measurements demonstrate an interface between BeO and InP substrates with high quality and efficient thermal stability. The use of ALD BeO as a gate dielectric may be a potential solution for future III-V MOS device fabrication.