The “self-organizing” of online crowds — or workers, more generally — into teams is a non-trivial problem of coordination and matching, in a context in which other parties are simultaneously competing for partners. Here, we experimentally investigate the capacity for workers in online crowds to self-organize into teams, within a scientific crowdsourcing contest. We compare matching outcomes and performance to those in a comparison group in which we eliminate the coordination and matching problem altogether (by directly assigning individuals to Pareto efficient teams). Online crowd members do remarkably well relative to the benchmark achieving 13% more functioning teams. Teams also tended to be more effective, by several measures. (We found no evidence these levels depending on the size of the self-organizing pool of workers.) Conditional on having formed, the self-organizing teams also benefit from several advantages in performance.