Origin has just debuted its Mac OS client, and it includes the "dual-play" feature for select titles in its library. Dual-play titles include both Mac and Win versions of the game, so if you buy either the Mac or Win version, you get both versions. I installed the client on my macbook just to see which of my BioWare game purchases are supported.
|Title||Is there a MacOS version?||Dual-Play|
|Dragon Age: Origins Ultimate Edition||Yes||No|
|Dragon Age: Origins||Yes||No|
|Dragon Age 2||Yes||Yes|
|Mass Effect 2||No||No|
|Mass Effect 3||No||No|
|Star Wars: The Old Republic||No||No|
As you can see from the table, the only BioWare title on Origin that is dual-play at the moment is Dragon Age 2. Searching the Origin store catalog, Dragon Age 2 is also the only BioWare title that is listed for purchase as both Mac and Win. Although Origin's dual-play support is currently limited, it's certainly a step in the right direction.