We found that in mice, following eye opening, fast-spiking, parvalbumin-positive GABAergic interneurons had well-defined orientation tuning preferences and that subsequent visual experience broadened this tuning. Broad inhibitory tuning was not required for the developmental sharpening of excitatory tuning but did precede binocular matching of excitatory orientation tuning. We propose that experience-dependent broadening of inhibition is a candidate for initiating the critical period of excitatory binocular plasticity in developing visual cortex.