In this study, five plant species, members of the Lamiaceae family, namely Salvia officinalis L., Salvia rosmarinus Spenn, Mentha × piperita L., Mentha spicata L. and Origanum vulgare subsp. hirtum (Link) Ietswaart, were studied for the influence of harvesting time on the herb crop yield, the volatile compounds (EOs) content/yield and their chemical composition. EOs were isolated by means of hydro-distillation from different plant parts at different growth stages. Their components were analyzed by gas chromatography coupled with mass spectrometry (GC-MS). The highest yields of EOs were obtained at the full flowering stage and important changes were observed in their composition. The fluctuations in the percentage composition of the major compounds in the EOs, throughout harvesting time, were observed at camphor/α-thujone for S. officinalis, camphor/1,8-cineole for S. rosmarinus, linalool/linalyl acetate and carvone/limonene for M. × piperita and M. spicata, respectively. The chemotype of O. vulgare subsp. hirtum was identified as carvacrol. The optimization of harvesting time could lead to increased crop production and better EOs quality control, with numerous industrial benefits upon the commercial production of such products.