Methylene-, ethylene-, and phenylene-bridged periodic mesoporous organosilicas (PMOs) synthesized with nonionic alkylethylene oxide templates exhibited significantly better mechanical and hydrothermal stabilities than periodic mesoporous silica. Synthesis of PMOs utilized the acid-catalyzed hydrolysis and condensation of bis(triethoxysilyl) precursors around supramolecular polyoxyethylene(10) stearyl ether (Brij 76) templates. Nitrogen gas sorption, thermogravimetry, and X-ray diffraction have been used to characterize the effects of aging, mechanical compression, and hydrothermal treatment on these materials. Both as-synthesized composites containing surfactant templates and extracted PMOs showed no degradation after 10 months. The enhanced stability of these nanoporous organosilicas relative to meoporous silica makes them potential candidates for use in advanced catalysis and adsorption applications.