We investigated overstable convective modes of differentially rotating massive main sequence stars. It is examined that the overstable convective modes in a rapidly rotating convective core may excite envelope non-radial oscillations by the resonance coupling between them. Let us denote by q the ratio of the angular velocity of the rapidly rotating core to that of the envelope. Then, it is found that as the ratio q increases, the order of the non-radial g modes resonantly coupled with the convective mode becomes lower, so that the excited g modes come to have shorter periods in an inertial frame. It is also found that when the separation of the frequencies of the consecutive envelope g modes is wider than the resonance width, there occurs the alternation between the strong and the weak resonances, i.e., the resonantly coupled mode becomes overstable or neutral according to the strength of the resonance.