Lucerne (Medicago sativa L.) is a major perennial forage legume worldwide. In Greece, new cultivars have been introduced mainly from the USA, Australia and Italy. However, some of these cultivars have not been tested locally before their widespread release. A field experiment was conducted from 2013 to 2016 in central Greece to compare the performance of 22 lucerne genotypes, including both local Greek and introduced genotypes, under irrigated Mediterranean conditions. There were three harvests in 2013 and five in each of the following years. Measurements included annual and total dry matter (DM) yield, harvest ratios, quality traits and agronomic parameters. Yields after the second year declined by 11.9–26.4%, possibly due to summer heat stress and reduced plant survival. However, several semi-winter-active cultivars were more persistent (by 19.4%) than highly winter-active cultivars. Three local, semi-winter-active cultivars and one introduced highly winter-active cultivar were the top performers for total DM yield (63.8–67.3 t DM/ha). Forage nutritive values showed small differences among cultivars. Evaluation of seasonal yield distribution was effective for comparing adaptive responses of genotypes in relation to the winter activity effect. Spring harvest ratio was more indicative (r = 0.92) of genotype total DM yield than was plant survival (r = 0.70). Specifically, highly winter-active cultivars showed higher autumn and spring harvests (by 36.4% and 7.9%, respectively) than semi-winter-active cultivars, which produced higher summer yields (by 35.7%). A regional program to breed more winter-active genotypes, which can capitalise on the longer preceding season with greater stand persistence, heat tolerance, summer productivity and height (>82 cm) and with more nodes (>18), could be beneficial for forage yield increase under the anticipated climatic changes.