A grab bar assembly includes a support beam adapted to be mounted to a vehicle and defining a longitudinal axis, a grab bar having an inner beam disposed within the support beam and movable relative to the support beam in first and second directions along the longitudinal axis. The assembly further includes a locking plate attached to the inner beam and a locking mechanism coupled to the support beam and having a latch movable between a lock position engaging the locking plate to fix the grab bar in a location relative to the support beam and a release position disengaging the locking plate to permit adjustment of the grab bar and the inner beam along the longitudinal axis in one of the first and second directions.