For the month of September, Xbox Live Gold members will receive four new free games – two on Xbox One and two on Xbox 360 – as part of the Games with Gold program. You can play both Xbox 360 titles on your Xbox One with Backward Compatibility.
On Xbox One, Xbox Live Gold members can download Earthlock: Festival of Magic ($29.99 ERP) for free during the month of September. Assassin’s Creed Chronicles: China ($9.99 ERP) will be available as a free download from September 16th to October 15th.
On Xbox 360, starting Thursday, September 1st, Forza Horizon ($19.99 ERP) will be free for Xbox Live Gold members through September 15th. Then on September 16th, Xbox Live Gold Members can download Mirror’s Edge ($14.99 ERP) for free through September 30th.
Source: Major Nelson