Hooker Henry Bell nabbed two tries and outside back Josh Whaanga grabbed a brace as well.
The game sprang to life in the second half.
Otago dominated the opening 40 minutes, but they were a little predictable on attack and were only able to crack the visitors’ defence once.
Hooker Ricky Jackson got in the boot of a lineout drive to score.
Finn Hurley had a tough introduction. He looked to get the ball wide early, but Southland winger Michael Manson picked it off and scampered 60 or so metres to score.
That was a rare highlight for the Stags who spent most of the game defending.
Otago rolled on an almost completely new backline for the second half and they were a lot more potent.
Ajay Faleafaga made some strong carries at second five. Sam Gilbert slotted in at first five and looked good as well.
His cross-field kick to Whaanga on the right wing was a classy touch.
Whaanga leaped high and somehow hauled it in when the ball was determined to escape his grasp.
Halfback James Arscott showed some good vision to put Whaanga in for a second in the same corner.
Play did not roll Jona Nareki’s way, but he made good use of his left boot.
And Bell, who is fresh from a stint in Major League Rugby, had a fine game.
Otago’s line speed on defence was good. Their driving maul was even better.
Overall it was a decent display ahead of their opening game against Tasman in Nelson on Friday.
Thomas Umaga-Jensen was a late scratching, though. And first-choice first five Cameron Millar did not get on. He is recovering from and ankle injury.
For Southland, prop Morgan Mitchell scored some points against his opponent in the opening half.
Winger Gabriel Hamer-Webb was industrious and powerhouse No 8 Semisi Tupou Ta'eiloa added some physicality when he came on.
But they were well beaten and have plenty to work on ahead of their opening game against Waikato in Invercargill on August 6.
Rep warm-up
The scores
Otago 31
Henry Bell 2, Josh Whaanga 2, Ricky Jackson tries; Sam Gilbert 3 con
Southland 7
Michael Manson try; Greg Dyer con
Halftime: 7-5 Southland.
