If you're looking to keep more EA games on Origin that you purchased off of Steam, you might be able to use some keys and activate the game on EA's service.
PC Gamer tried some keys
and found a few worked, but some like Mass Effect
did not. Most of the newer titles didn't have any issues. Now, I was able to activate some EA titles that I purchased from the store on Steam so going one way was possible, but now it seems some games allow you to go the other way as well with games purchased on Steam being able to be activated on Origin.
I didn't like having a couple online distribution services running on my computer, but I guess I will have to with the word that Battlefield 3
won't be making an appearance on Steam.