A 34th-minute try from Ben Youngs and a 100 per cent kicking record from Owen Farrell saw The Lions head to Newcastle with their unbeaten record intact but the Reds ran them close, just as Gatland and co had predicted in mid-week.
With Youngs sneaking over from the back of an opposition five-metre scrum and Farrell adding three penalties and a conversion, the Lions led 16-9 at half time after Luke Morahan had grabbed the game's first try with a fine individual effort.
Nick Frisby crossed for a second score for the Reds as conditions deteriorated after the break but Farrell saw The Lions home with two more penalties as he finished with a personal tally of 17 points.
The Reds begun brightly in Brisbane, twice going close through chip and chase efforts down the left-hand side in the first three minutes. They came even closer to opening the scoring before five minutes were on the clock as only last-ditch tackles prevented Ben Tapuai and then Rod Davies from crossing the line.
The Lions sprung to life with eight minutes gone as Alex Cuthbert came within an inch or two of finishing off a stunning solo run from fellow wing Tommy Bowe. Bowe sliced through a host of defenders after taking an inside switch off Jonathan Davies following turnover ball deep inside Lions territory but Luke Morahan forced Cuthbert into touch as he dived for the line. The French referee asked for clarification from the TMO but Cuthbert's reaction told the near sell-out crowd all they needed to know.
The deadlock was eventually broken by a well-taken Farrell penalty from wide on the right after 13 minutes but it was the Reds who celebrated the game's opening five-pointer as Morahan added to his defensive heroics with a wonder score five minutes later.
The Qantas Wallabies wing, who picked up his solitary Test cap against Scotland in June 2012, claimed Farrell's up and under close to his own 22 before evading Cuthbert's tackle and plotting his way to the line. Morahan's arching run took him wide of skipper Sam Warburton and in between Ben Youngs and Mako Vunipola before a deft chip over the top of Stuart Hogg and a kind bounce straight back into his hands allowed him to touch down underneath the posts.
Reds captain Quade Cooper added the straightforward extras and the Reds were 7-3 to the good with 18 minutes played as the Queensland faithful raised the already impressive noise levels inside the venue for the first Test.
The Lions then lost Manu Tuilagi to injury shortly after Morahan's score, with Welsh wing George North coming on at outside centre. North was immediately involved in the action as he chased Jonathan Davies' kick ahead after a loose pass from Cooper but the pace of the ball took it over the dead-ball line before he could claim his first try in Lions colours.
Farrell closed the gap to a single point with a second penalty from an almost identical angle to his first on 23 minutes, with Cooper missing the chance to re-establish the Reds' four-point advantage with a simple strike just past the half hour mark.
Cooper's blunder was the start of an eventful few minutes for Britain and Ireland's elite as Farrell went agonisingly close to his side's first try before halfback partner Youngs touched down just moments later.
Turnover ball provided the initial platform for Richie Gray to find space inside his own half, with the Scotland lock passing the ball on to Ben Youngs who then found North wide on the left. North skipped past the first attempted tackle before flipping the ball inside to the supporting Farrell, only for that man Morahan to knock possession from his grasp as he reached for the line.
The Lions' didn't have to wait long for their deserved score, however, as Youngs pounced from the back of the resulting scrum. The Leicester No9 capitalised on confusion at the setpiece between Jake Schatz and Nick Frisby to dot down for a simple score that pushed The Lions back in front at 11-7.
Farrell's sweetly struck conversion moved the tourists six points clear and they continued to dominate the closing stages of the half as they kept up the intensity levels that assistant coach Rob Howley had spoken so much about during the week.
Warburton became the third Lion to see a TMO decision go against him within reach of the tryline after Cooper and Anthony Faingaa got their bodies beneath the line and the ball following a sensational break from North. The 21-year-old picked up a Reds kick ahead just inside his own 22 before racing inside and then out to leave the Reds defence in pieces. North then found his national captain with a wide pass but Warburton still had plenty to do against two backline defenders who eventually prevented what would have been a truly memorable try.
The Lions did at least add to their points tally before the break , though, as Farrell made it four successes from four attempts courtesy of straightforward penalty after Tapuai failed to roll away having brought down Tom Youngs 25 metres out.
A fourth Farell penalty widened the nine-point interval lead to 12 with half an hour left to play before heavy rain ensured the remainder of the game wouldn't feature quite so much free-flowing rugby as the first 50 minutes.
A lengthy stoppage after a clash of heads with Vunipola saw Reds openside Beau Robinson's game brought to a premature end added to the broken rhythm of the third quarter but it was the Reds who reacted the stronger as Frisby raced over for a second Queensland score.
The man starting at scrum-half in the absence of Qantas Wallabies lynchpin Will Genia touched down after taking an inside ball from Davies once the right wing had raced down his touchline and into The Lions' 22.
Frisby's effort cut the gap to a single score at 19-12 but Mike Harris - the centre who robbed Wales of a famous win over Australia in Melbourne with a brilliant late penalty this time last year - missed the easy extras to ensure his side still needed a converted try to draw level with 15 minutes remaining.
Both sides continued to try and attack with ball in hand but it was Farrell's boot that eventually sealed the win for The Lions as he coolly slotted another penalty with just three minutes remaining.
There was still time for the Reds to push for a third try but committed defence from the tourists prevented that from happening and ensured The Lions will face a combined New South Wales Queensland Country side on Tuesday knowing they could be four from four by the time they take on the Waratahs in Sydney a week today.