Can Steam be used to Launch Mass Effect 3?

It is possible to launch Mass Effect 3 through Steam, but you still need Origin to load the game. I just tested this myself by:

1. Clicking Add A Game in the bottom left of the library tab
2. Add a Non-Steam Game
3. Browse...
4. Local Disk --> Program Files (x86) --> Origin Games --> Mass Effect 3 --> Binaries --> Win32 --> MassEffect3.exe

Now when I launch the application from Steam, it launches Origin which then launches Mass Effect 3. Launchception.

Note that I am playing from a Windows Computer running Windows 7 64-bit, so the names of your exact directories will differ by OS/depending on how you set up your Origin installation.

If you were hoping to access your Steam Overlay within the game, this will require a bit of a workaround.

Instead of having a direct shortcut to ME3, you will have to create a shortcut to Origin:

1. Clicking Add A Game in the bottom left of the library tab
2. Add a Non-Steam Game
3. Browse...
4. Local Disk --> Program Files (x86) --> Origin --> Origin.exe

Make sure Origin isn't currently running, then launch it from Steam. Now, when you launch any game from this instance of Origin, you will be able to access the Steam overlay. Screenshot of my ME3 with the Steam Overlay here.

If you want to get fancy, you can also rename the shortcut (to Mass Effect 3) as well as change the icon to ME3's to replace the default Origin one:

Both overlays will be available (assuming they are on different key bindings). Be aware, however: opening the Origin overlay will pause the game, but opening the Steam overlay will not. Further, when both overlays are opened at the same time, the steam overlay cannot be interacted with (the origin overlay pops up on top of it).

Well, you don't need to do all of that.

At least now, with the latest Steam & Origin installed. Mass Effect 3 is already available under the Add a non-Steam game option

Just select it & click on Add Selected game.

Click on play to launch it. Works with or without Origin running before launching Mass Effect 3. Note that your Steam status will mention you're playing Mass Effect if you don't exit Origin after exiting Mass Effect - shouldn't make much of a difference though.