Shani Arona, the No 2 Otago golfer, was the star of the team when she came from behind, winning the 17th and 18th hole to secure the match.
She beat Katrina Manaena, who three-putted the seventeenth green and encountered bunker trouble on the final hole.
Otago No. 4 Riho Kanazawa already had a win in the bag, playing the last hole one up and putting the result beyond doubt with a well executed par on the final hole.
Fourteen-year-old Laura Hoskin putted well to give Otago its second win, downing the experienced Fiona Murray by an impressive 4 and 3 margin.
For Southland, the evergreens Robyn Pullar and Lisa Henderson won their games at the expense of Monina Tulisis (No.1) and Kathryn Fletcher (No.3).
Beating Southland was a milestone for the Otago women as the southern neighbours have held the Salisbury Cup, the measure of annual competition, for almost a decade.
But in the afternoon, Otago went down to Hawkes Bay-Poverty Bay by a 2 to 3 margin, with four matches going the full distance.
Kanazawa won 16 and 17 to beat Kathy Olsen on the final green, while Fletcher was always ahead of Janie Field, also winning on the final green.
Tulisi struggled in the afternoon, going down to Kate Chadwick on the sixteenth green.
Arona almost holed her approach to the final green but finished one down when she halved the final hole with Jaime McIvor.
Hoskin turned one down to Angela Jones but fought back to lead by one with four holes to go.
However, she came to the final hole one down and halved the hole with Jones in pars.
The tournament is shaping up to be a top-of-the-north battle, with defending champion Waikato and North Harbour remaining unbeaten in one division, just ahead of Northland, while last year's runner-up, Auckland, and Bay of Plenty are unbeaten in the other division.
The only "outsider" in with a strong chance after two days is the young Wellington team, which recovered from a loss to Auckland yesterday morning to post a convincing victory over Southland.
Waikato was made to work for its 3-2 morning win over Manawatu-Wanganui, but then whitewashed Taranaki 5-0 for its third successive win.
Waikato has a big day today against Tasman and North Harbour.
After a bye yesterday morning, North Harbour was in supreme form with a 5-0 result over Canterbury, led by 12-year-old Lydia Ko at No 1, who was 4-under when she completed a 7 and 6 win over Anita Harkerss.
Nestled in third placed in this division is Northland, which halved its match with Canterbury in the morning before beating Manawatu Wanganui 4-1.
On the other side of the draw, Auckland enjoyed two wins with a 3 to 1 effort over Wellington in the morning followed by a convincing 5-0 effort against Aorangi South Canterbury.
Bay of Plenty was untroubled to account for Aorangi South Canterbury 5-0 in the morning, with most of the matches finishing well before time.
Wellington was outgunned in the morning by Auckland, but showed fortitude to fight back convincingly over Southland in the afternoon to share top standings, on six points, with Auckland and Bay of Plenty.
There are two rounds today and the final round-robin games tomorrow.
