What attracted so many supporters of the Occupy Wall Street movement to the movement’s Facebook pages? Using a database of 1500 Facebook Occupy group pages, we analyze the types of posts that recruit new users. In the case of the Occupy movement, the success of recruiting over 400,000 users to Facebook was driven by user-created content produced in a medium that encourages contributions and sharing to an existing set of dense networks of potential movement sympathizers. We find that the posts that are most successful at recruiting active Facebook engagement utilize existing forms of communication, such as sharing pictures and status updates. We also find that posts that use confrontational messages and messages about solidarity appear most often in the top posts. Our findings suggest that online social networking tools such as Facebook and Twitter provide a powerful tool for movements to rapidly spread information and reach broad audiences. In addition, we offer some analysis of the impact of these findings for social movements that hope to utilize Facebook.