Usual hooker Richard Puddy, playing at openside flanker, scored the first of Gladstone's five tries after crashing over following a lineout. The conversion attempt by fullback Inia Katia was easily charged down.
Greytown extended their lead when slippery winger Nick Robertson won a kick and chase to score in the corner.
Puddy then scored his second try when he swooped on a loose Greytown lineout throw.
Poor Gladstone discipline also led to three Southey penalties, giving Greytown a deserved half-time lead.
If Gladstone were just hanging on in the first spell, the second half was a different story.
The in-your-face approach of the Gladstone forward pack rattled Greytown, and the Gladstone backs, especially the elusive Katia, took full advantage.
Two minutes into the half, he hit the gap from a scrum and sprinted 30 metres to score in the corner.
He was back in the action 13 minutes later, when he latched on to a poor clearing kick and went on a jinking 30-metre run that ended with impressive replacement halfback Charlie Bargh dotting down handy to the posts.
And if that was not enough, the little Fijian dived under some desperate Greytown defence to give Gladstone the lead for the first time, with five minutes to play.
Katia, Puddy and experienced No8 John Stevenson stood out in a solid all-round performance by the home team.
For Greytown, the forward pack failed to gain any dominance.
The backs were clearly missing key players, although Olsen showed his class with several telling runs.
Pioneer continued their good run of form with a convincing 41-15 defeat of Eketahuna at Jeans St. Pioneer ran in five tries to two, in an entertaining clash.
Marist had to work hard to quell a strong East Coast forward effort at Whareama. Shannon Lewis crossed for two of Marist's four tries in the 22-14 victory.
First-five Tim Priest showed his class as Martinborough over-ran Carterton 23-7. The former West Coast Heartland's representative scored 18 points from a try, three penalties and a conversion.
Gladstone 32 (Richard Puddy 2 tries, 2 con, pen; Inia Katia 2 tries; Charlie Bargh try) Greytown 31 (Carlos Rimene try, Nick Robertson try, Jordan Oakey try, Abe Southey 2 con, 4 pen)
Pioneer 41 (Jayden Mason try, Karl Thompson try, Lee Ewe try, Shane Harmon try, Nikora Ewe try, Joe Thompson 2 pen, 5 con) Eketahuna 15 (Tom Mueli try, pen; Penalty Try, Dylan Bennett con)
Marist 22 (Shannon Lewis 2 tries, Pua Tufa try, Ayden Eruera try, Keiran Te Whare con) East Coast 14 (Jack Watt try, Jeff Gibson try, Utah Walker 2 con)
Martinborough 23 (Tim Priest try, 3 pen, 2 con; Hemi Davis try) Carterton 7 (Trent Hopwood try, Andy Humberstone con)
Senior Reserve results
Masterton Red Star 33 East Coast 5
Marist 50 Eketahuna 7
Greytown 35 Gladstone 0
Pioneer 28 Tuhirangi 14
