South Otago finished the top qualifier in the Highlanders First XV competition after the final round of games on Saturday.
Needing to win and pick up a bonus point, South Otago beat Central Southland 42-8.
In the other crucial game on Saturday, Southland Boys hit form to beat Dunstan 50-10 and qualify for the top four.
Otago Boys and Waitaki Boys are the other two teams to qualify for the top four of the Zero Fees-sponsored competition.
They clashed last week, with Otago Boys winning 22-12.
In next week's first round of pool games in the top section, South Otago plays Otago Boys in Dunedin, while Waitaki Boys travels to Invercargill.
In other results on Saturday, Kings beat John McGlashan 32-5 and Gore beat St Kevins 24-3.
Verdon just finished ahead of Kavanagh, 19-18, to make the middle four along with Dunstan, Gore and Kings.
The teams play each other once in their section before the finals of the competition, which is also sponsored by the Otago Daily Times, on August 22.
