A flexible barrier assembly having a flexible visible light-transmissive substrate having a Tg greater than or equal to that of heat-stabilized polyethylene terephthalate (“HSPET”) overcoated with a first polymer layer having a Tg greater than or equal to that of HSPET and further overcoated with at least two visible light-transmissive inorganic barrier layers separated by at least one second polymer layer having a Tg greater than or equal to that of HSPET can be used to mount, cover, encapsulate or form moisture- and oxygen-sensitive articles such as organic light emitting devices and light valves.