Southern slotted a late penalty to defeat Kaikorai 23-21 in a thrilling match at Bishopscourt.
Green Island and Harbour were locked 23-23 at Miller Park before loose forward Brett Kingsbury scampered down the touchline in the final moments to score and seal the win for the home side.
Alhambra-Union ran out 38-0 winners against Zingari-Richmond at the North Ground.