If used in succession with other protection moves, it has a 50% chance success rate. Unlike Protect, which works on all moves, Quick Guard prevents all effects from moves with a heightened Speed Priority. In addition to that, it also protects all the player's Pokémon on the field rather than just the user.
However, even though it blocks all moves with a Speed Priority of 1 or higher, it does not block moves increased in speed priority by the ability Prankster. In addition to that, the move Feint will hit through this move, as it does with Protect and Detect.