Here is the list of free games available on the Xbox 360 and Xbox One to Gold Members only, for the month of September. Don’t forget you can save lots of money on Xbox Live Gold Membership and Microsoft credit here
On Xbox One, Xbox Live Gold members can download Prison Architect: Xbox One Edition for free during the month of September. Livelock will be available as a free download from September 16th to October 15th.
On Xbox 360, starting September 1st, LEGO Star Wars III: The Clone Wars will be free for Xbox Live Gold members through September 15th. Then on September 16th, Xbox Live Gold Members can download Sega Vintage Collection: Monster World for free through September 30th.
SOURCE : MAJOR NELSON