Cox then lost to Mudra Lakhani to tie things up and leave it down to Jo Taylor.
Taylor held her nerve on the final hole against Tania Hook to give Northland their second win on the opening day.
The result sparked interest not only around the club, but around the region as they look to win for the first time.
Northland's third outing pitted them against Taranaki, who had picked up one win in their first two matches.
Jacoby again led from the front as she picked up a comfortable 6&5 win over Celeste McLean. She was joined in the winner's circle by Cox who grabbed an equally impressive 5&4 result against Kim Lucas.
Despite May going down comfortably, Bulkeley and Taylor halved their contests to give Northland the win.
Auckland were next on the agenda and look to be one of the front-runners. With six of the last eight Toro titles in their trophy cabinet, they were always going to be a tough prospect for the home side.
They proved their pedigree by grabbing a comfortable 5-0 win with Jacoby, Bulkeley, Taylor and Jenny Peters all going down heavily.
Meanwhile the men's Toro Interprovincials kicked off at Mangawhai Golf Club and Northland quickly set about their work.
In their first outing they thumped Tasman 4.5-0.5 in a statement performance but were defeated 4-1 by Waikato in the afternoon.
Christian Nitsche and Kadin Neho grabbed matching 5&4 wins against Tasman with Luke Brown and Alex Neely also getting wins.
However the match with Waikato proved tricky for the home side with only captain Scott Wightman gaining a win.
Northland next take on Wellington and Manawatu/Whanganui in the men's competition while the women face Aorangi in the morning before having a bye round to close the day.