An ORVR valve assembly operative of relatively few movable components includes a valve body, having conduits to provide for routine passage of vapors therethrough through operations of a vacuum assist system. This is when a non-ORVR vehicle is being replenished with fuel. But, when a vehicle equipped with ORVR vapor recovery is being fueled, vacuum is generated above a piston supported diaphragm, attracts the diaphragm upwardly, plugs off the vapor passage conduits, and allows the ORVR system of the automobile to exclusively treat the generated vapors at the location of the vehicle and its fuel tank. Simultaneously, air is vented into the valve body, below its diaphragm, and into the vapor return line of the vacuum assist system, to prevent it from being subject to excessive vacuuming. Thus, vapor recovery or treatment can be achieved through the use of the ORVR valve assembly of this invention, regardless whether the automobile being refueled is an ORVR equipped vehicle, or one that is not equipped with vapor recovery.