The Lions had to overcome stubborn opposition and difficult wet conditions to maintain their unbeaten start to the tour after three games.
A delighted Gatland, said: “They showed some great character. That’s what playing for the Lions is all about. We soaked up the pressure.
“I am really proud of that performance. We missed out on a couple of opportunities with a couple of tries that were very close.
“They kept digging deep when it was required. There were a couple of poor passes missed, but that’s rugby.”
The victory was tainted with the news that Irish winger Tommy Bowe will play no further part in the tour after breaking a bone in his hand. He is the third player to head home early after countryman Cian Healy and Wales prop Gethin Jenkins were forced out through injury.
Gatland said: “We probably will bring someone out. It’s a huge blow because Tommy brings experience and the ability to play left wing, right wing, centre and full-back. It’s a huge loss for us.”
In testing conditons, several players left the field from the physical nature of the game. Lions centre Manu Tuilago departed with a shoulder injury while Jonathan Davies and Mako Vunipola took heavy bangs while Queensland Reds duo Beau Robinson and Ben Lucas both left the pitch on stretchers.
The Reds played with furious pace from the outset and immediately had the tourists on the backfoot but the Lions were on the scoreboard first through Owen Farrell’s boot.
But Reds winger Luke Morahan stunned the Lions with a brilliant individual try when he evaded Alex Cuthbert and Sam Warburton, before gathering his own chip over Stuart Hogg to touch down under the posts. Cooper converted, and then Tuilagi departed after just 20 minutes to be replaced by Wales wing George North, who went into midfield alongside his countryman Jonathan Davies.
A second Farrell penalty narrowed the gap to a point, before the Lions hit the front through Youngs who robbed Reds No 8 Jake Schatz of possession close to the line.
Farrell kicked a fourth penalty 10 minutes into the second period, before Reds scrum half Nick Frisby waltzed over. Mike Harris missed the easy conversion before Farrell sealed victory with his fifth penalty.
