The optical light curves of the three symbiotic stars AG Dra, AX Per and AG Peg, in the U, B and V photometric bands, in the quiescent states of these stars, are interpreted on the basis of a “reflection” model for the observed light variations. A least squares fit of a numerical model that is constructed to the observed magnitudes of the stars yields the value of few of the orbital elements of these binary systems. Some predictions are made on the basis of the model and its parameter values about the detailed structure of the light curves of the three stars, and of the expected structure of radial velocity curves of the cool components in these systems.