1) Open Origin and enter its settings menu (click the gear symbol in the top right corner).

2) Navigate to the In-game tab.

3) Uncheck Enable Origin In Game. Select Done.

4) Exit Origin (right click tray icon > Exit).

5) Open Steam and navigate to the Library window.

6) Select Add a game... > Add a Non-Steam Game.

7) Select Browse and locate Origin.exe (default location: C:\Program Files (x86)\Origin\Origin.exe).

8) Make sure Origin is checked on the Add a Game window and select Add Selected Programs.

9) Launch Origin through the new shortcut in your Steam library and launch Battlefield through Origin.

http://pcgamingwiki.com/wiki/Battlefield_3