A versatile flow synthesis method for in situ formation of organozinc reagents and subsequent cross-coupling with aryl halides and activated carboxylic acids is reported. Formation of organozinc reagents is achieved by pumping organic halides, in the presence of ZnCl2 and LiCl, through an activated Mg-packed column under flow conditions. This method provides efficient in situ formation of aryl, primary, secondary, and tertiary alkyl organozinc reagents, which are subsequently telescoped downstream to a Negishi or decarboxylative Negishi cross-coupling reaction. The described method offers access to a variety of C-C bond formations with organozinc reagents that are otherwise commercially unavailable or difficult to prepare under traditional batch reaction conditions.