Webb partners Matthew Morgan at half back with Ben John and Jonathan Spratt in the centre.
Bridgend full back Jamie Murphy gets a chance to impress for the region at his home ground.
With Steve Tandy missing a number of players due to international and under 20 call ups, the Ospreys head coach is looking to his younger players to step up to the mark.
"This is the start of a crucial period for us," said Tandy.
"We are minus nine players away with the senior squad, seven with the U20s, and there are a number of key players still on the injury list so it is this group of players who will be looking to build some momentum over the coming weeks.
"One thing you can guarantee with this group is they will give everything for the cause in these games and will leave nothing out on the field."
Tandy, who was previously in charge of the Ravens, is looking forward to taking his side back to the Brewery Field to take on the leaders of the Aviva Premiership.
"Sunday is a big day and big occasion for both the region and for Bridgend in particular, with the best team in England coming to the Brewery Field," he added.
"With seven Bridgend boys in the starting line-up I'd expect to see the Bridgend public turning out to get behind their region. I know the boys can't wait to play there again.
"Playing games like this in Bridgend also allows youngsters a chance to watch their region at their local rugby club and that can only be a positive thing."
Sunday's LV=Cup clash will be a tough test for a young Ospreys side and Tandy knows his side will have to be at their best if they are to secure the win.
"Harlequins will provide a really difficult test for us. They aren't top of the Premiership, current champions and top seeds in Europe for nothing," he argued.
"The players know what is expected of them and that they need to be at their best if we are going to get the level of performance needed to get anything out of this match."