Whaanga banged over the penalty from a handy angle with less than five minutes to go in the match at Carisbrook to draw 3-3 with Canterbury Metro and give Otago the title on countback from Southland.
Both teams finished equal on the top of the table with 18 points but Otago won the grade as it had beaten Southland 13-7 earlier in the season.
In other results in the grade yesterday, Canterbury Country thrashed North Otago 55-0 and Southland beat South Canterbury 52-0.
In the under-65kg grade, Canterbury Metro confirmed it was the top team with a convincing 31-3 win over Otago.
It finished with the maximum 25 points in the competition, having won all its games with bonus points.
Canterbury Country beat North Otago 66-0, while South Canterbury and Southland drew 7-7.
Otago finished third in that grade, just behind Canterbury Country.
North Otago won the fair play award in both grades, its teams congratulated for their sportsmanship despite not winning a game.
Four Otago players made the starting XV in the under-48kg tournament team named after the matches yesterday: prop Max Pennell, lock Hayden Dyer, Whaanga and winger Josh Vou. Midfield back Jayden McLew and No 8 Logan Jenkins made the reserves.
Canterbury Metro dominated the under-65kg tournament team, with nine of its players selected in the starting XV.
Otago second five-eighth Patelesio Tomkinson made the side, as did prop Hamish Taylor. Hooker Joseph Cairns and fullback Chris McNoe were selected in the reserves.
