Gloucester produced a magnificent second-half performance to run out comfortable winners over Harlequins at the Twickenham Stoop.

After trailing by 10 points at half-time, the visitors looked a completely different side in the second period, as they scored tries through the outstanding Peter Richards, replacement hooker Olivier Azam and number eight James Forrester.

Former Otago Highlanders fly-half Willie Walker, playing in place of the injured Ryan Lamb, collected a 16-point haul from two conversions and four penalties to send the travelling Gloucester faithful home happy with the 31-21 win.

Gloucester director of rugby Dean Ryan will be delighted with his side's second-half display, while his opposite number Dean Richards will be concerned in equal measure with his team's slipshod tackling and lack of bite up front.

Quins scored tries through Ceri Jones and a late effort from Simon Keogh, while former All Black fly-half Andrew Mehrtens kicked 11 points, but the west-London side have now lost two from two and are in serious need of a morale-boosting win on their return to the Guinness Premiership. They travel to Wasps next week.

The opening stages saw little rugby of any real quality as both sides struggled to hold on to possession in the contact.

England scrum-half Richards provided the main threat for the visitors, shrugging off an early knock and proving a constant threat around the breakdown.

One Richards break led to Walker's opening penalty on five minutes after Quins had encroached offside.

An uncharacteristic missed penalty from Mehrtens gave the Gloucester fans something to laugh about, but they were less amused when the former All Black found his range with two well-struck efforts to make it 6-3 after 26 minutes.

The visitors' mood darkened even further when Quins prop Jones scored the opening try of the game in the 28th minute, his second in the space of a week.

Steve So'oialo's break, direct from the restart, created space for former South Africa captain Andre Vos down the right. The number eight fed the ball inside to Nicolas Spanghero who in turn fed the supporting Jones to crash over for a superb try. Mehrtens' conversion extended the lead to 13-3.

The two fly-halves exchanged further penalties before half-time to make it 16-6 at the break.

Gloucester flew out of the blocks in the second-half with Andy Hazell looking odds-on to score in the 43rd minute, only to be denied by a brilliant try-saving tackle from Keogh.

The visitors continued their resurgence, with Richards seemingly at the heart of everything.

Walker closed the gap to seven points with his third penalty before Richards added a superb individual score when he shrugged off three Quins defenders to scoot in from 45 metres. Walker levelled proceedings at 16-16 after 48 minutes.

The Gloucester fly-half took them in front with his fourth penalty and Azam extended the visitors' lead to eight points in the 63rd minute when he scooped up the ball at the side of the breakdown and thundered over in the corner.

Forrester made the game safe in the 67th minute when he took advantage of some more sloppy Quins defending to score down the blindside after Gloucester cleverly wheeled the scrum. Walker's conversion made it 31-16.

Keogh's late effort added some closed the gap to 10 points but there was no masking Gloucester's superiority.