Superconducting properties of Y-Ba-Cu-O compounds have been studied by examing the behavior of microwave induced dc voltages. The oscillatory dependences of the induced dc voltages as a function of amplitude and frequency together with the polarity reversibility indicate that these materials consist of Josephsoncoupled superconducting grains. We have observed the microwave induced dc voltages in the transition region (80-90 K) of a single-phase Y1Ba2Cu3O7 sample as well as at much higher temperature (up to 240 K) in a mixed-phase Y1.8Ba0.2CuO4 sample.