Dunedin clawed back a 10-point deficit to beat University 33-22.
Taieri concluded its season with a 29-22 win against Alhambra-Union and Zingari-Richmond edged Green Island in a 30-28 thriller.
Southern: 31
Kaikorai: 7
Southern flung the ball wide and scored five cracking tries - true story.
The Magpies have got to the top by rumbling the ball up through their massive forward pack and their backline has been an afterthought.
But the side must have picked up the wrong script because it played a more expansive game to beat Kaikorai 31-7 at Bathgate Park.
The game was billed as a dress rehearsal for the semifinal and Kaikorai will be concerned after it was outplayed in most facets.
It did hold on to the ball for longer periods during the second half but made too many errors to mount a serious challenge.
Southern revealed another side of itself and the spark came from an unexpected source - halfback Mackenzie Haugh.
He has mostly played on the wing this season but slotted in behind the scrum and shocked onlookers with a marvellous 25m pass straight to winger Ben Leggett, who galloped 40m to score in the opening moments of the game.
Bryce Hosie had a good game at first five-eighth and dotted down twice in the first half to give Southern a 19-0 lead at the break.
Prop Mike Mata'afa made some strong runs in his 100th game, and Leggett scored a second to stretch the lead to 26-0.
Kaikorai responded with a Blair Tweed try. But Haugh finished as he started with a stunning skip pass which found loose forward Adam Knight in the centre of the field. He plucked the ball out of the air and charged 35m for a superb try.
Zingari-Richmond: 30
Green Island: 28
Zingari-Richmond withstood a late charge from Green Island to record a thrilling 30-28 victory at Miller Park.
With one round remaining in the competition, and both sides out of playoff contention, players from each team were prepared to make the most of their opportunities.
On a dry ground this could have made for a high-scoring affair, but the heavy underfoot conditions and a slippery ball made for a high error rate as both teams were given ample voice from large support bases on each side of the field.
Zingari-Richmond scored the first of its five tries when Chris Bell dived over in the 20th minute.
Green Island replied in kind soon after through Alex Barnsley but, just as it appeared the home team could begin a scoring spree with its pack beginning to dominate, handling errors and defensive lapses let Zingari-Richmond back into the game, and it hit back with two tries in quick succession for an 18-11 lead at the break.
Green Island's halftime pep talk spurred it into life and its passes began to go to hand, leading to two tries and handing it a five-point advantage heading into the final 10 minutes.
But it was Zingari-Richmond's bench players who began to make a difference up front and, after a sustained assault on the Green Island line, the visiting side eventually found the gaps for two tries in three minutes.
Behind by seven points, the final five minutes belonged to a desperate Green Island.
A try to captain Hayden McBride lifted its confidence and provided it with every opportunity to snatch victory, but it was not to be, with two attempts at three-pointers, and victory, going to the left of the posts.
Taieri: 29
Alhambra-Union: 22
Aggressive running up the middle by veteran halfback Kurt Hammer was the key to Taieri's second-half comeback at the North Ground.
In the first spell, the Alhambra-Union forwards dominated the lineout and pushed Taieri back in the scrums to give their fleet-footed backs space.
Fast-running fullback Jona Nareki scooted in for the first try after three minutes and broke the defensive line late in the spell allowing wing Jerry Garfula scored for Alhambra-Union to lead 15-7 at halftime.
Taieri changed tactics after the break and attacked with the forwards close to the ruck and maul.
The constant barrage worked as Taieri scored four second-half tries and 22 points to win the game. It started when centre Matt Whaanga split the defence from his own 10m and Josh Casey scored in the corner.
The powerful Taieri forwards, led by lock Vinnie O'Connell and No8 Riley McDowall, were difficult to stop as they drove together inside the Alhambra-Union 22m.
Hammer had the strength of a tank and was in his element when he scored tries after 28 and 31 minutes to level the scores at 22-22.
The Taieri pack continued its onslaught and McDowall crashed over for the winning try five minutes later.
The other Taieri backs to impress were first five-eighth Josh Casey and hard-tackling Kori Rupene in the midfield.
The best Alhambra-Union forwards were Jacob Coghlan, who took six clean lineouts takes and was quick to the breakdown, and fellow flanker Alistair Burnett.
Dunedin: 33
University: 22
University started this game with a hiss and a roar and knew it was playing for its most important trophy of the season in the Johnny Keogh Memorial at the University Oval.
It had eight points on the board in the blink of an eye with a long-range try to fullback Gavin Stark off a slashing Thomas Umaga-Jensen break and a penalty to flyhalf Dominic Clapcott.
Dunedin brought a sense of parity to the game when winger Mone Samate-Paul dived over out wide after a prolonged build-up to cut the lead to three.
That just spurred Varsity as it took control. It looked hungrier in the loose and its backs were prepared to go wide with the well-won ball.
It was rewarded with two more tries, the first to midfielder Umaga-Jensen, who scampered 40m to score, and the second when prop Callum Hardie crashed over after a series of drives.
University led 22-5 late in the first spell and the game looked done for Dunedin. But the visiting side came back with a late try to prop Don Brighouse off a deflected pass to cut the lead to 10 at the break.
There must have been whisky in the Dunedin water at halftime as it came out breathing fire in the second spell. It scored two quick tries to put its noses in front and never looked back.
The first was off a kick-pass from first five-eighth Louis Tili who found Samate-Paul out wide and he fed blindside flanker Ashley Craig who dotted down. The second was to replacement midfielder Fapene Popoaili'i who crashed over from a big lineout drive from the Dunedin pack.
The Dunedin scrum was monstrous and terrorised the Varsity eight.
Its pick and go game wore down Varsity and fullback Tim Cossens capitalised and kicked three penalties to give it an 11-point lead and make the game safe.
For Dunedin, front rower Teague McIlroy was powerful on the burst and really came of age in this game.
He was well supported by fellow prop Don Brighouse who was his normal industrious self.
Hame Toma, as per usual, was a menace with ball in hand and he dominated in the loose in the second spell.
He was well supported by other loosies Ashley Craig and Jamie Mowat.
For Varsity, No8 Sione Teu was far and away his side's best and made some telling breaks. Umaga-Jensen and Stark were dangerous out wide and both scored nice tries with power and pace.