A chair leg mountable coaster assembly includes a plate that is mountable to one of a plurality of legs of a chair. The plate extends laterally from the leg in a single direction that is orientated parallel to a plane that extends through bottom ends of the plurality of legs. The plate is one of a plurality of the plates, each of which is configured to be mountable to a respective one of the plurality of the legs so that each leg is engaged with one of the plates. The plates reduce penetration of the legs into a soft substrate, such as sand, dirt, and soil. The plates are sized to allow multiple ones of the chairs to be stacked without interference by the plates.