Occupy Wall Street organizers said Friday they were preparing a series of events—some potentially disruptive—to mark the one-year anniversary of a protest movement that for weeks focused the world's attention on a tiny park in Lower Manhattan.

After months of operating mostly outside of public view, organizers predicted that thousands would converge on Washington Square Park on Saturday for a day of "education" and for a union-backed concert in Foley Square on Sunday. Organizers said they would try to block access to the...