To enable Steam in game you must launch Origin with Steam, AND have in game overlay Disabled in Origin settings.

To launch Origin with steam just go to your steam library and click add non-steam application and find origin.exe.

To disable in game overlay; launch origin and go into origin settings(the gear icon), and click settings, then click the "in game" tab and uncheck the enable origin in game checkbox.

BF3 Platoon[battlelog.battlefield.com]