His addition to the Scarlets rugby environment provides a timely boost to the West Wales squad after losing a number of players to international duty during the Six Nations and with some key RaboDirect PRO12 games ahead.
The Scarlets have three tough domestic league fixtures this month travelling to Treviso this weekend, followed by Ulster away and then to return home for a big Parc y Scarlets fixture against Edinburgh on Saturday 22nd February (kick off 2.30pm)
The 32-year-old experienced back who can play both in the centre and at outside half has won 23 caps for England since his debut in 2001. His most notable spell of his professional club career was at Bath, with 161 appearances and 1,447 points during his two spells with the club;as well as time with Gloucester and then French Top 14 club Racing Metro.
Barkley was born in London and grew up in Cornwall.
Scarlets Head Coach Simon Easterby said: "Olly will bring a lot of experience to our squad both from his distinguished test and club career in England; he can cover 12 and 10 and will add much needed cover for usas we have so many players unavailable during the international call ups as well as some long term injuries we have in midfield.
"We are very pleased he is joining our set-up at Parc y Scarlets, there was obviously a lot of interest from clubs in the UK looking to securing him after he left Grenoble. It will be a boost and give our team added depth at an important time in our season as we look to kick on in our domestic league. It's obvious he's keen to get onto the field and perform well and get some competitive game time under his belt."
Barkley, who has worked with former Ireland coach Mark Tainton who is based at Parc y Scarlets until the end of this season said: "I'm excited to be joining the Scarlets for the rest of the season and looking forward to getting plenty of game time after a frustrating period at Grenoble.
He added: "I know Mark Tainton from earlier on in my career and once I'd spoken to him about the set-up at the Scarlets and had the opportunity to work with him and Simon Easterby, who I have a lot of respect for as a player and coach, it was a very exciting prospect. The Scarlets squad has some fantastic players and I hope I can add something in the coming months and I look forward to working with Simon and his coaching team and joining the players to try and be part of an ambitious team keen make an impact for the rest of the season."
Olly Barkley was released from his contract with Grenoble by mutual consent between player and the French club. He had joined the club as their marquee singing at the start of the season from Racing Metro.