Its 66-37 win was also the product of a midcourt which worked just a tad harder.
Zoey Flockton made some nice touches at wing attack and Sophie Erwood's height at wing defence created problems for her opponents.
She also made a couple of cracking passes up court to goal attack Eden Millan, who shot well with 28 goals from 34 attempts.
Fellow shooter Madeleine Hunt (31 from 43) was also fairly accurate and the pair combined to snaffle quite a few rebounds when they missed.
Southern goal keep Tarryn Dickson was instrumental on defence for Southern. She picked off three or four intercepts, made several crucial deflections and was always lurking dangerously.
Markham's College shooting pair of Isabella Masani and Kiana Pelasio did not enjoy the same space as Southern enjoyed at the other end.
The College midcourt struggled to get the ball up court and feed their shooters, although wing attack Sophie Napper floated in some quite delightful passes and was impressive in the midcourt. Grace Carruthers was tidy at goal defence as well.
College was hampered by injuries which stymied its flow. It had its best period early in the third period when it traded goals with Southern.
But the Magpies dominated the majority of the match. Southern got out to a 9-2 lead early, after capitalising on some errors from College. It led 18-11 at the first break and extended its lead to 34-20 by halftime.
The Magpies worked hard towards the end of the third quarter to stretch their buffer by a further three goals.
The final period was one-way traffic with Southern winning the quarter 18-6.
In the other premier A matches, St Hilda's Collegiate beat newly promoted Phys Ed Blue 55-32. Kate Heffernan had a strong game at centre for the school side and team-mate Meg Timu made a valuable contribution at goal defence.
The South Pacific Titans, who have also just been promoted, stuck with PhysEd A in the opening quarter but the competition leader pulled away to win 64-47.
University Albion A beat Phys Ed B 71-53. It was a comfortable victory in the end but there were just three goals separating the teams at halftime.
