Up to now, V382 Cyg and TU Mus are the only two discovered O-type overcontact binary stars with periods less than two days (P=1.8855 and 1.3873d). Both systems contain a visual companion. New eclipse times and analyses of orbital period variations of the two systems are presented. It is discovered that the periods of both binaries show cyclic oscillations with periods of 47.70 and 47.73yr, while they undergo continuous increases at rates of dP/dt=+4.4x10^-7^ and +4.0x10^-7^d/yr, respectively.