South Sydney is bound for September action after wrapping up a top-eight spot and sending North Queensland's home-final hopes into disarray with a dramatic 20-10 win at Stadium Australia.
The Cowboys dropped to third place on the ladder as a result of the loss, allowing Cronulla to move into second spot.
The Sharks beat Canterbury 16-0 earlier on Saturday evening, while Canberra surged into the top eight after thrashing Manly 48-6.