The Volts resumed day two at 141 for four and reached 339 thanks to a fine innings of 83 from Jesse Ryder and solid contributions from Jimmy Neesham (59), Mark Craig (41) and Derek De Boorder (38).
In reply, Wellington rattled on some relatively quick runs, reaching 210 for three at stumps.
Michael Pollard is undefeated on 79 and James Franklin (16) is at the wicket with him.
Volts pace bowlers Jacob Duffy and Blair Soper might be the future of Otago cricket but they struggled to restrict Wellington's top order scoring rapidly.
Soper bowled four no balls in six overs and conceded 49 runs. He is going for more than eight an over. Duffy was frugal by comparison, coughing up 37 runs from his seven overs.
Neesham, who claimed his maiden five-wicket bag against Northern Districts last week, also found the going tough, conceding 38 runs from seven overs.
All-rounder Sam Wells did his part to slow the onslaught. He nicked out Stephen Murdoch (30) and removed the dangerous Michael Papps (58 from 63 balls).
When spinner Nathan McCullum came on, the run rate slowed dramatically. The experienced offspinner bowled 15 overs for just 21 runs and picked up the wicket of Grant Elliott.
At 132 for three, Wellington's innings was teetering a little but Pollard and Franklin added 78 without further loss.
Earlier, Ryder resumed on 39 and looked on track for a third century this season before he was bowled by former Black Caps spinner Jeetan Patel.
He had combined in an 83-run stand for the sixth wicket with Neesham, who followed Ryder into the shed six runs later.
De Boorder and Craig added a valuable 72 for the eighth wicket to guide the Volts past 300.
Meanwhile, Martin Guptill warmed up for the limited overs series against the West Indies in fine style, but his century may not be enough to save Auckland from defeat in Napier.
In his first Plunket Shield match of the summer, Guptill stroked an unbeaten 135 on the second day of the clash against Central Districts, saving his side from a huge first innings deficit.
But the Stags still lead by 194 runs and Guptill is running out of partners. Auckland had reached 273 for seven at stumps. In Christchurch, leader Canterbury is in pole position to grab another victory after responding to Northern Districts' 172 with 382 yesterday to build an imposing lead of 210 runs. At stumps, ND was 61 without loss.
- Additional reporting by APNZ.
