Working memory requires large-scale cooperation among widespread cortical and subcortical brain regions. Importantly, these processes must achieve an appropriate balance between functional integration and segregation, which are thought to be mediated by task-dependent spatiotemporal patterns of correlated activity. Here, we used cross-correlation analysis to estimate the incidence, magnitude, and relative phase angle of temporally correlated activity from simultaneous local field potential recordings in a network of prefrontal and posterior parietal cortical areas in monkeys performing an oculomotor, delayed match-to-sample task. We found long-range intraparietal and frontoparietal correlations that display a bimodal distribution of relative phase values, centered near 0° and 180°, suggesting a possible basis for functional segregation among distributed networks. Both short- and long-range correlations display striking task-dependent transitions in strength and relative phase, indicating that cognitive events are accompanied by robust changes in the pattern of temporal coordination across the frontoparietal network.