Objective: The large scaffold protein bassoon is a central component of the presynaptic cytomatrix at the active zone (AZ), the site where vesicles release their neurotransmitter content. Deletion of bassoon has been reported to impair AZ formation and to partially silence synapses, but its molecular role remains largely unclear. Here, we investigate cerebellar mossy fibre to granule cell synapses, which are characterized by rapid vesicle recruitment at a limited number of release sites, in control and bassoon knockout mice. Methods: We recorded spontaneous miniature EPSCs, EPSCs evoked by low-frequency stimulation, and EPSCs during and following trains of high-frequency stimulations at individual MF-GC connections. Results: Basal synaptic transmission was normal in bassoon knockout (bsn^-/-) compared to control mice. During sustained synaptic transmission, however, synaptic depression was more pronounced in bsn^-/- mice. In addition, recovery from depression was slower compared to control. Quantitative analysis indicated that the release probability and the number of readily releasable vesicles were normal but that the rate of vesicle recruitment was reduced by ~30% in bsn^-/- mice at both room and physiological temperature. Conclusion: These results provide evidence that bassoon supports vesicle recruitment at the AZ of glutamatergic central synapses.