The genus Origanum, which includes many species and subspecies, is widespread in the whole Mediterranean area. In this study, Origanum onites individual plants collected from 18 different localities of three different cities of West Anatolia (Antalya, Izmir, and Mugla) were grown and some of their agronomic characters and essential oil contents were determined. The 75 Origanum onites lines selected from 1362 single plants were evaluated for plant height, herb yield, essential oil content, and oil components. The highest dry and fresh herb yields were obtained from the Antalya-Manavgat-Side clone and the highest essential oil content (4.1%) was found in the Mugla-Bodrum-Yalikavak clone. Six different chemotypes were identified in the lines. In general, carvacrol was the main component in the A clones; only one locality from Antalya-Kalkan had high linalool content as the main component of all clones.