This paper demonstrates a novel quadstable monolithic mechanism (QsMM), which provides four stable equilibrium positions within its planar operation range. The QsMM has been realized from the use of both - and -directional bistable structures, which utilize curved snapping beams. Two pairs of curved beams were attached to an inner frame in both and directions to present an independent bistable behavior in the directions. It was found out that the design of the inner frame is crucial for the quadstability and dynamic responses of the mechanism. A millimeter-scale brass mechanism was actually fabricated by ultraprecision milling to test the quadstability and the force-displacement behavior. The prototype clearly demonstrates four distinct stable positions in its millimeter-scale operation range. The design concept, finite element simulation, fabrication, and experimental measurement of the proposed multistable mechanism have been presented. The mechanical multistability of the proposed QsMM can be utilized for multiple switching and optical networking applications, yielding low power consumption operations.