Garlic is widely cultivated for both its culinary and medicinal properties. Bulb yield, organosulfur compounds, and plant mineral nutrition of 32 garlic varieties were characterized. Across genotypes, there was large variability in bulb weight and alliin and allicin concentrations. The mineral concentration of a reference leaf was strongly positively correlated with bulb weight (for Zn, N, and K) and bulb allicin concentration (for S, Mo, and Cu). Alliin represented ∼61 and 88% of the total clove S content. In situ synchrotron-based X-ray absorption near-edge structure (XANES) analysis identified two dominant S compounds, γ-l-glutamyl-S-allyl-l-cysteine and alliin. Stoichiometric studies showed the ratio of conversion of alliin to pyruvate was consistently below the theoretical 1:1 ratio, while the ratio for conversion of alliin to allicin was consistently higher (∼1.9:1 to 3.5:1). A combination of optimized fertilizer management and genotype selection for high alliin can potentially substantially increase the yield and medicinal quality of garlic.