We present the first bistable 2 × 2 crossbar switches using dual suspended nanobeams with phase changing Ge₂Sb₂Se₄Te₁ (GSST) cladding material. The dual suspended nanobeam configuration gives a higher-temperature pulse that will efficiently change the phase of a nanoscale GSST cladding on each nanobeam cavity region. The compact resonant 2 × 2 Mach–Zehnder switch has stable cross and bar states corresponding to the amorphous and crystalline phases of the GSST, respectively. We have optimized the nanobeam design using 3D FDTD and have made detailed numerical simulations that predict low insertion loss and low crosstalk with ∼100 GHz bandwidth. Finally, the application of this device to N x N x Mλ wavelength cross-connect switching is presented. The unique integration of switch design elements presented in this paper enables, for the first time, the combination of nonvolatile resonant behavior, low switching power, low insertion loss and crosstalk, wide bandwidth, and fast switching times, for WDM switching applications.