Peel, who started all three Tests for the Lions in New Zealand six years ago but missed out on squad selection in South Africa, will be given an opportunity to push his World Cup claims in the capped Millennium Stadium encounter.
And with Gatland having already described the fixture as a 'trail' game for openside flanker Williams, the same is likely to apply to Peel.
The Sale scrum-half has started just two Tests in the last two years and has often been overlooked for a place in the matchday 22.
Peel, who currently has 76 caps to his name, looks set to go head-to-head with former Scarlets team-mate Mike Phillips, the man who replaced him as the Lions Test starter two summers ago.
The outcome of the battle could have a significant impact on Peel's hopes of travelling to New Zealand in the autumn, with Gatland having selected Tavis Knoyle ahead of Peel in his squad for the first of five World Cup warm-up matches.
As well as Welshmen Peel, Williams and Iestyn Thomas, the Babaas side will also include Italian captain Sergio Parisse, Wallaby back row George Smith, All Black prop Carl Hayman and Springbok trio Ruan Pienaar, Francois Steyn and Joe van Niekerk.
Peel's fellow Lions John Hayes, a tourist in 2005 and 2009, and Iain Balshaw, a 2001 Test cap, is also included, as is giant French centre Mathieu Bastareaud.