Otago centre Opini Toomalatai breaks through the tackle of Southland's Rocky Pettigrew at Tahuna Park on Saturday. Photo by Craig Baxter.
The juniors overcame a 16-13 half-time deficit to win 36-22, while the senior team turned around a 60-16 loss last year to win 64-4.
Otago was too strong for Southland, breaking the defence at will, and the contest was over by the break.
The side never dropped its effort in defence, working hard until the 80th minute to mow down Southland breaks.
Coach Grant Leoni said his players made an "unbelievable" effort, and played with passion against a big side.
"The Southland side was a big, monster side, but our boys gave it to them."
Leoni picked prop Rawiri Kahukiwa and half Tasi Cordtz for special mention, and said their play reminded him of New Zealand Warriors captain Steve Price and former Kiwi Stacey Jones.
