During early postnatal brain development, experience-driven delivery of AMPA receptors to synapses participates in the initial organization of cortical function. By combining virus-mediated in vivo gene delivery with in vitro whole cell recordings, we identified a subunit-specific developmental program of experience-driven AMPA receptor delivery to synapses in rat barrel cortex. We expressed green fluorescent protein (GFP)-tagged AMPA receptors (GFP-GluR1, or GFP-GluR4) into layer 2/3 pyramidal neurons at two distinct developmental periods, postnatal day (P)8–P10 and P12–P14. Two days after viral infection, acute brain slices were prepared, and synaptic transmission from layer 4 to layer 2/3 was analyzed by whole cell recordings. We found that whisker experience drives GluR4 but not GluR1 into these synapses early in postnatal development (P8–P10). However, at P12–14, GluR1 but not GluR4 is delivered into synapses by whisker experience. This precise developmental plan suggests unique plasticity properties endowed in different AMPA receptor subunits which shape the initial experience-driven organization of cortical function.