The present disclosure provides for a loading unit for use with and/or supportable on a distal end of a surgical stapling apparatus. The loading unit includes a housing portion including a distal end and a proximal end, a drive assembly slidably supported within the housing portion of the loading unit, and a locking mechanism supported on the housing portion of the loading unit. The locking mechanism has a first position wherein the locking mechanism engages the drive assembly and maintains the position of the drive assembly in a ready-to-load position relative to the housing portion of the loading unit. The locking mechanism is pivotable to a second position wherein the locking mechanism disengages the drive assembly and enables the drive assembly to move relative to the housing portion.