Peel missed Wales' entire autumn Test series, but he enjoyed an impressive 30-minute return during Llanelli's Powergen Cup victory over Sale Sharks last Friday.
He is now poised for an intriguing battle opposite his fellow Lion, Wasps scrum-half Matt Dawson.
Peel replaces Clive Stuart-Smith, while other changes will include starts for Welsh internationals Lee Byrne, Matthew Watkins and Alix Popham, with Gareth Bowen preferred to Mike Hercus at fly-half.
"We've had a lot of work to do this week, and we know that we have to front up if we are to face the challenge that awaits us this weekend," said Scarlets rugby director Gareth Jenkins.
"They (Wasps) are without doubt a formidable side with a reputation for having an invincible defence. Our challenge on Sunday will be to break and fracture that defence."