Neuronal oscillations can effectively support transient communication across brain structures. Here I report that 4-Hz oscillation temporally coordinates task-related neuronal activity in the medial prefrontal cortex (PFC), hippocampus and ventral tegmental area (VTA), in rats performing a working memory task. The working memory component of the task was associated with a prominent increase of power and coherence of the 4-Hz and gamma oscillations in the PFC and VTA. Importantly, gamma oscillations of both structures were locked to ascending phases of 4-Hz oscillation, forming cross-frequency coupling between 4-Hz and gamma oscillations in working memory periods. Subsets of both PFC and hippocampal neurons predicted the future trajectory of the rat. A significantly larger fraction of goal-predictive PFC pyramidal neurons were better phase-locked to both the 4-Hz and hippocampal theta oscillations than non-predictive cells. The 4-Hz and theta oscillations were phase-coupled at their troughs and jointly modulated the amplitude of local gamma oscillations and neuronal firing in the PFC, VTA and hippocampus. These findings demonstrate that timing of spikes in the PFC-VTA-hippocampus axis is temporally coordinated by both PFC 4-Hz and hippocampal theta rhythms and, at a finer scale, by gamma oscillations in support of working memory.