Alumina-Ordered Mesoporous Silica (OMS) hybrid membranes were synthesized by using the evaporative induced self-assembly (EISA) process based on dip-coating of commercial macroporous alumina substrates with a Brij-56/TEOS/HCl/H2O solution. Two different commercial alumina membranes are used here as macroporous supports: Whatman Anopore and Pall Membralox. The former is scientifically interesting but not so practical for industrial use due to low mechanical strength, while the latter is a more practical route to a commercially useful product. Numerous analytical methods are used to probe both the hybrid material and the silica phase after dissolution of the alumina substrate. Most importantly, He/N2 permeation measurements show that the effective pore size of the membrane can be tuned from 20 to 5 nm based on the number of dip-coating cycles used. The observed He/N2 permselectivity is nearly identical to the theoretical Knudsen value, which is ascribed to the lack of pinhole defects in the materials. The silica obtained after dissolution of alumina substrate has been characterized using scanning and transmission electron microscopy. Those results indicate that the silica deposited in the membrane possesses ordered pores approximately 5 nm in size, consistent with the permeation studies. The current work presents an alternative approach to materials that possess many of the properties of mesoporous silica thin films (i.e. pores of controlled size and topology) without the difficulty of growing mesoporous silica thin films on porous supports.