A surgical fastener applying apparatus includes an end effector assembly having an anvil assembly and a cartridge assembly. The anvil assembly and/or the cartridge assembly is movable relative to the other between open and closed positions. The cartridge assembly is configured to retain a plurality of surgical fasteners therein. A fluid-actuated drive assembly including a distal piston member is configured to oscillate between proximal and distal positions. The distal piston member includes a base and a rack extending distally from the base and slidably disposed within the cartridge assembly. A drive beam is configured for translation through the cartridge assembly to eject the surgical fasteners from the cartridge assembly. A pawl assembly couples the drive beam to the rack such that the drive beam is incrementally advanced along the rack and through the cartridge assembly as the distal piston member oscillates between the proximal position and the distal position.