Selecting and planning actions recruits neurons across many areas of the brain, but how ensembles of neurons work together to make decisions is unknown. Temporally coherent neural activity may provide a mechanism by which neurons coordinate their activity to make decisions. If so, neurons that are part of coherent ensembles may predict movement choices before other ensembles of neurons. We recorded neuronal activity in the lateral and medial banks of the intraparietal sulcus (IPS) of the posterior parietal cortex while monkeys made choices about where to look and reach. We decoded the activity to predict the choices. Ensembles of neurons that displayed coherent patterns of spiking activity extending across the IPS--'dual-coherent' ensembles--predicted movement choices substantially earlier than other neuronal ensembles. We propose that dual-coherent spike timing reflects interactions between groups of neurons that are important to decisions.