We report the ability to control the atomic structure of nanoclusters by systematically varying the gasphase formation parameters during the generation of size-selected Au-923. From aberration-corrected, scanning transmission electron microscopy (HAADF-STEM) imaging, we are able to identify the proportions of icosahedral (Ih), decahedral (Dh), and face-centered cubic (fcc) isomers within a set of populations, with each population corresponding to a specific set of formation conditions. We demonstrate that, by tuning the formation conditions, we can eliminate completely all icosahedral nanoclusters, which are commonly found under other conditions. In future, this approach may lead to the preparation of arrays or ensembles of nanoclusters containing a dominant or single isomer, thus enabling the investigation of nanocluster (or nanoparticle) properties as a function of both size and atomic configuration.