Both he and Munn are back this year, joined by leading Castlecliff Golf Club player Tyler Lock, along with Tyler Hodge and Junior Tatana.
After the first round bye on Tuesday, Manawatu-Wanganui beat Poverty Bay 4-1, coming from three wins and two draws.
They then started Wednesday morning with a convincing 5-0 win over Hawke's Bay, before being held to a draw with Northland in the afternoon, 2-2. That contest went down to the last hole with the No1 players Munn and Kadin Neho halving their match to share the points.
"It was a really tough match and we are pretty happy to get a half," said Neho, the 2013 New Zealand Amateur Champion.
He made a clutch birdie on the par four eighth [his 17th] to get his team back into the contest and then they halved the last in pars. Both teams therefore stayed unbeaten, although there was improvement as Manawatu-Wanganui lost to Northland last year 3-2.
They then made a good start to Thursday, beating North Harbour 3-1.
McDonald had won all four of his matchups at this point.
Munn got off to a fast start, being three under through five holes to be three up, and he never relinquished the advantage to beat Jason Gulasekharam 5-3.
"I saw on the board on five that all the boys were going well and it got me pumped up a bit," said the 23-year-old from the Manawatu Golf Club.
Munn said the experience of contending and winning the championship last year at the North Shore should prove invaluable in the final two days.
Heading into yesterday afternoon, Manawatu-Wanganui were leading Division 1 ahead of Wellington and Northland.
The semifinalists from Division 2 are likely to be decided out of Bay of Plenty, Otago and Waikato teams.
The Toro NZ Women's Interprovincial will follow the men's event from December 9 - 13 at the Riverside Golf Club.