It is the Grizzlies' first appearances in the playoffs since 2002, and a remarkable turnaround considering the team played a promotion-relegation game against West Taieri just two years ago.
Taieri secured top spot with a tight 17-15 win against a University side missing half a dozen regular starters. It will host Green Island in one semifinal, while University will be at home to Harbour, who had a bye on Saturday.
Kaikorai pummelled Zingari-Richmond 74-24 but narrowly missed a playoff spot, while Southern beat Alhambra-Union 40-33 in the other game.
Green Island - 31
Dunedin - 24
With 31 minutes gone in the second spell and the game locked at 24-24 and the Dunedin pack dominating the game, Green Island's season looked done.
Then in a blink of an eye it all changed when Dunedin went wide on halfway.
It threw a loose pass which was latched on to by right winger Isaak Te Hiwi.
He scorched 48m and duly converted to put Green Island into its first playoff game since 2002.
The crowd went nuts at the Toolbox and ancient props were dancing jigs in the in-goal in an outpouring of emotion.
Dunedin were shattered, especially its pack, which ``owned'' the Green Island eight for most of the game.
The game's two best players were in the Dunedin pack, where openside flanker Hame Toma was all aggression and power and terrorised his opposites at times.
Spare a thought for big prop Teague McElroy, who scored all four Dunedin tries and was left lamenting they did not prevail.
How McElroy is not in the Otago set-up is a complete mystery, as he has been the best prop in the back half of the season.
Dunedin led 19-17 at the break, following three McElroy tries; he was unstoppable from close range.
Green Island had its moments and scored tries through loose forwards Jesse Va'ausuaga and Brett Kingsbury.
Te Hiwi's goal kicking was exemplary and he kept the game close.
Dunedin lost Toma late in the first spell to the bin, and Green Island capitalised when Dunedin pulled down a scrum close to its own line - Green Island was awarded a penalty try.
McElroy was not to be denied after 16 minutes in the second half when he crashed over for his fourth.
The game was stalemated at 24-24, before Te Hiwi's heroics.
Kingsbury stood out at blindside for Green Island, while James Arscott's distribution skills were impressive at halfback.
Southern - 40
Alhambra-Union - 33
Not much defence to see here.
Two teams with nothing left to play for but fun entertained with some running rugby.
Tackling was optional at Bathgate Park, and Southern's superior forward pack eventually came to the fore.
The Magpies collected a 40-33 win and outscored their opponents six tries to five.
Winger Owen Draper nabbed three tries. But Alhambra-Union centre John Tapueluelu matched Draper's production with three of his own.
His side also picked up two bonus points, which was enough for it to move ahead of Zingari-Richmond in the standings and avoid the wooden spoon.
Draper's third try was something to see. He showed a lot of pace and did an in-and-out on the AU defender to score out wide.
He was on the end of the chain for his first. There was some poor defence leading up to that one, though. And for his second, he simply outstripped the defence.
Tapueluelu had to work harder for his triple. He had to drive to the line for one of them and force his way through several defenders.
AU openside Jacob Coghlan had an industrious match and also got on the score sheet.
And both goalkickers were accurate. Mackenzie Haugh drilled five conversions for Southern, while Levi Emery nailed four.
Southern No8 Mika Mafi had a quiet opening 40 minutes, but came into the game more in the second spell.
AU was without captain and hooker Alex Frood, and the team missed his presence in the scrum in particular.
Taieri - 17
University - 15
Taieri is one supremely organised outfit - and in this game, it had to be.
The Eels absorbed a lot of pressure to secure a 17-15 win against a University side missing six regular starters at the University Oval.
Taieri's win clinched the Gallaway Trophy and secured top billing for the playoffs.
Both sides look destined to meet in the final. They are the two of the better defensive units in the competition, and those attributes were on proud display.
Taieri led 6-3 at halftime thanks to the boot of Corey McKay.
There were a lot of big hits in the opening 40 minutes. University had more of the ball and spent a lot of time in its opponent's half.
The second half did not open up much at all. Defence dominated proceedings, but the key moment came eight minutes into the spell.
Williams collided with Taieri winger Marc Rooney in the air.
Both were focused on the high ball, but Williams had a duty of care and got a yellow card.
Taieri was able to convert its numerical advantage into five points. Prop Kieran O'Sullivan burrowed over from a lineout drive.
But University struck back just before Williams' return.
The pack battered away at the line for yonks before the ball was moved quickly to the left to winger Chris Johnston.
But two late penalties saw Taieri establish an unassailable 17-8 lead with three minutes to go.
University got a late consolation through winger Calvin Vari.
Kaikorai - 74
Zingari-Richmond - 24
It was too little, too late for Zingari-Richmond when it suffered what appears a heavy 74-24 defeat at the hands of Kaikorai, at Montecillo.
The home side got away to an inauspicious start, losing a man to the bin in the first play of the game. No sooner had it returned to its full complement when it scored a try through flanker Junior Meafua.
But Zingari-Richmond's resurgence was short-lived, as Kaikorai hooker Sam Wyber began a scoring spree that removed all hope of an upset.
Wyber played a key role in shutting the home side down, and setting up numerous scoring opportunities, scoring the first of his three tries from a 30m burst through the Zingari-Richmond defence. And while his second try came from a rolling maul, it was his third that put the home side on the mat and down for the count. He made a 40m burst down the touchline, with would-be tacklers left lying in his wake.
Trailing 57-5 at the break, Zingari-Richmond found itself staring down the the barrel of a humiliating defeat to end the season. But on came its bench, and Kaikorai found itself up against a vastly different side in the second spell. It was a period of play that heartened the Montecillo faithful. The home side found its mojo to score three further tries and put some respect back in the scoreline.
Apart from Wyber, Kaikorai was well-served by flanker Jake Russ, lock Isimeli Tuivaga and first five-eighth Roman Blackman. For Zingari-Richmond front rowers Reita Puatolo, Bailey Matoe and Alex Nettleton and flankers Jacob Turrell and Meafua featured.
PLAYERS OF THE WEEK
University v Southern
Jack McHugh (U) 3
Josh Brown (T) 2
Corey McKay (T) 1
Southern v Alhambra-Union
Owen Draper (S) 3
Jacob Coghlan (AU) 2
John Tapueluelu (AU) 1
Zingari-Richmond v Kaikorai
Sam Wyber (K) 3
Jake Russ (K) 2
Roman Blackman (K) 1
Green Island v Dunedin
Hame Toma (D) 3
Teague McElroy (D) 2
Brett Kingsbury (GI) 1
Round 17
The scores
Taieri 17 (Kieran O’Sullivan try; Corey McKay 4 pen), University 15 (Chris Johnston, Calvin Vari tries; Mike Williams con, pen). Halftime: Taieri 6-3.
Kaikorai 74 (Sam Wyber 3, Jordan McEntee 2, Sam Jones 2, George Thomas 2, Isimeli Tuivaga, Rowan Gouws, Sam McCall tries; Roman Blackman 7 con), Zingari-Richmond 24 (Junior Meafua 2, Reita Puatolo, Alex Nettleton tries; Scott Hunt 2 con).
Halftime: 57-5.
Southern 40 (Owen Draper 3, Axel Hohneck, Jermayne Maika, Riku Kitahara tries; Mackenzie Haugh 5 con), Alhambra-Union 33 (John Tapueluelu 3, Jacob Coghlan, Kevin Vaeluaga tries; Levi Emery 4 con). Halftime: 28-19.
Green Island 31 (Jesse Va’ausuaga, Brett Kingsbury, pen try, Isaak Te Hiwi tries; Te Hiwi 3 con, pen), Dunedin 24 (Teague McElroy 4 tries, George Witana 2 con). Halftime: 19-17 Dunedin.
