Just a week out from the first Test against the All Blacks, tries from Will Greenwood, debutant Ryan Jones and the electric Shane Williams were enough to keep the Lions' juggernaut rolling, with Charlie Hodgson kicking 15 points.
And a number of players made a telling case for inclusion in the Lions' 22-man squad for the Christchurch Test - most notably the Welsh number eight Jones who only arrived on tour as a late replacement for Simon Taylor but produced an excellent all-round performance.
The Lions have been forced to work hard for their tour victories so far, and it was no different as they were forced to hit back from 13-6 down.
Otago boast a fearsome reputation as Lion-tamers, forged through victories in 1950, 1959, 1966 and 1993, and they started fastest and sharpest.
Four penalties in the opening 11 minutes allowed Otago, who dominated possession of the ball in the opening exchanges, to work a 6-0 lead as the Lions took their time to find their shape.
Otago winger Matt Saunders took advantage of some lax defence on the short side to plough deep into Lions territory and Donncha O'Callaghan strayed offside in an attempt to clear his lines.
Nick Evans slotted the penalty, struck the post with another just minutes later and then doubled Otago's lead after being felled by a high tackle from Lions debutant Jones.
It was only then, a quarter of an hour into the game, that the Lions finally retained some possession and they built effectively through the phases to earn the penalties that allowed Hodgson to level the game at 6-6.
The Lions looked to expand their game but Hodgson spilled an inside ball from Greenwood and Denis Hickie slipped an offload forward to Geordan Murphy.
Otago, who had spent 10 days in camp ahead of the game, were attacking with more precision.
Neil Brew, the Maori winger, burst through Hickie's tackle and then bounced off Hodgson to send scrum-half Danny Lee scampering over in the corner.
The Lions needed a score before the interval and it took one piece of opportunism to bring them level.
Hodgson, standing over a penalty two metres in from the left touchline, spotted Greenwood in space on the opposite wing and launched a surprise cross-field kick that bounced kindly for the England centre to level matters once again.
Evans, the capped All Black fly-half, was a livewire threat for Otago and after being caught with another high tackle, this time from Martyn Williams, he opened the second half by slotting Otago ahead again.
But the Lions began to exert some authority up front and when Shane Williams darted across field he found Jones, enjoying an excellent debut, on a direct run to the line.
The converted score earned the Lions a lead for the first time and after Evans had reduced it to 20-19, Sir Clive Woodward sent on the heavy artillery with Andrew Sheridan, Steve Thompson, Danny Grewcock and Matt Dawson introduced with 20 minutes remaining.
The new heavyweight pack immediately put Otago under pressure with a surging rolling maul, Hodgson calmly slotted the penalty and the Lions then created their best score of the tour.
Jones sparked the attack with another charging run through the middle and then a sweeping back move, featuring quick hands from Greenwood and the newly-introduced Ollie Smith, sent Murphy clear before Shane Williams applied the clinical finish.