Oat (Avena sativa L.) is a cereal widely grown as a spring crop throughout the temperate zones, being particularly adapted to areas with cool and wet summers such as Northwest Europe and Canada. There is scope for further oat expansion in Mediterranean Basin where the crop will face hot and dry weather. In this work, we assessed adaptation of 32 modern oat cultivars from different origin and usage to autumn sowings under Mediterranean agroecological conditions. Experiments were carried out over four crop seasons at 6 contrasting locations along Mediterranean Basin, including Spain, Tunisia, Egypt and Palestinian Territories. ANOVA analysis revealed genotype × environment interactions. For test environment and genotype evaluation heritability-adjusted genotype plus genotype × environment (HA-GGE), biplot analysis was performed. Biplot analysis differentiate two mega-environments one comprising the locations of Egypt and Palestinian Territories and another including Spain and Tunisia. Pearson's correlation and HA-biplots confirmed overall a positive correlation between yield and HI, and a negative correlation between yield and rust and flowering date. For other traits, relations among the traits differed depending on the ME evaluated. The study allowed determining within each ME the best discriminative location, representative of the target environment and repeatable across year and the genotypes with superior and stable characteristic for breeding of adapted oats.