Embodiments of the invention provide an adjustable barrier assembly for enclosure, and related methods of installation. The adjustable barrier assembly includes a barrier panel that includes a first panel slidable relative to a second panel to accommodate different depths of different enclosures. The assembly further includes a top support bracket, an upper barrier plate, a bottom support bracket, and a lower barrier plate. Each of the upper barrier plate and the lower barrier plate can be secured to the top support bracket and the bottom support bracket, respectively, at different relative orientations in order to accommodate different heights of different enclosures.