I'm guessing you're talking about Infinity, since Reccomended is 1.8.2 and Beta is 1.9.0.
If you use the Curse client right-click the Infinity profile, select the "..." button, open the "profile settings" and select "Beta" instead of "Released". On FtB there's a drop box where you select the version (I've moved completely to Curse so if someone else can supply the specifics?)
Or, as an easy way out, you can wait until sometime next week when, barring issues with 1.9.0, it'll be moved to "Recommended" status.