We have measured the magnetoresistance of a dc superconducting quantum interference device in the form of an interrupted mesoscopic normal metal loop in contact with two superconducting electrodes. Below the transition temperature of the superconducting electrodes, large h∕2e periodic magnetoresistance oscillations are observed. By adding a small dc bias to the ac measurement current, h∕4e oscillations can be produced. Lowering the temperature further leads to even larger oscillations, and eventually to sharp switching from the superconducting state to the normal state. This flux-dependent resistance could be utilized to make a highly sensitive flux detector.