Can't find how to assign post to multiple groups

It was working fine earlier today but I must have changed a setting somewhere and I can't figure out how to change it back so that it works again... When I was creating new "pages" earlier today there was an option for Organic Groups to make the page viewable for multiple groups - basically, it let me choose the audience that could see this page. I'm not sure what I did but now that option doesn't appear on the content types that are set to Standard Group Post. What needs to be set so that this option reappears?