By computing Andreev scattering coefficients for a three-dimensional disordered solid containing superconducting inclusions and evaluating a generalized Landauer-Buttiker formula for the two-probe electrical conductance G, an intuitive result is obtained for the dependence of G on the phase of the superconductors. For the simplest case of two inclusions, it is shown that G varies periodically with the phase difference phi of the superconducting islands, with period 2pi. For more than two inclusions, beating can occur. It the superconductors are decoupled, G varies periodically with time, at the Josephson frequency. If the superconductors are weakly coupled, this behaviour is preceded by a time-independent regime in which phi increases with the externally applied voltage, while G changes non-monotonically. It is demonstrated that at least in the presence of single-channel external leads, the ensemble averaged conductance of a highly disordered system varies periodically with period 2pi, in contrast with a periodicity of pi found for weakly localized systems.