Scientists have developed efficient gene editing systems for many economically important crops, like rice (Oryza sativa), wheat (Triticum aestivum), tomato (Solanum lycopersicum), maize (Zea mays), and soybeans (Glycine max). However, progress in onion (Allium cepa) has significantly lagged these major species. As the second most produced vegetable crop worldwide, onion breeders and researchers would greatly benefit from the development of a robust and efficient gene editing platform. To date, only one published study has demonstrated successful CRISPR/Cas9-based editing in onion, highlighting both the technical recalcitrance of onion and the urgent need for improved editing strategies. This dissertation presents an efficient CRISPR/Cas9 gene editing system for onion using biolistic delivery of gold nanoparticles harboring editing reagents and plasmid vectors designed to enrich for gene editing in the population of regenerated plants. The approach is built upon three key components: 1) Delivery of pre-complexed Cas9/gRNA ribonucleoproteins (RNPs), which bypasses the need for transient expression or stable integration of DNA encoding Cas9 and sgRNAs. 2) Co-delivery and transient expression of morphogenic regulatory genes to enhance proliferation of transfected cells and support recovery of edited lines. 3) Co-delivery and transient expression of a Hygromycin phosphotransferase gene to confer transient resistance in transfected cells during a short term Hygromycin selection period. This system enables the recovery of transgene-free, gene edited lines from plants regenerated through tissue culture. The ability to produce transgene-free edited onions is especially significant, as these lines are often preferred over transgenic counterparts from both scientific and regulatory perspectives.