There is still an ambiguous opinion on oat regarding its safety for people with celiac disease (CD). Some studies have confirmed different content of oat immunoreactive epitopes in different cultivars while others explain the differences in consequence of cross-contamination with gluten-rich species or as ELISA cross-reactivity of oat homological epitopes with antibodies against wheat gliadin. Our study was based on a two-year mapping of oat immunoreactive epitopes in a set of 132 oat cultivars using the G12-based ELISA kit. Although repeated evaluation confirmed high interannual variability (RSD ≥ 30%) in approximately 2/3 of the cultivars, the permitted gluten content (20 mg kg-1) has not been exceeded except for contaminated cultivar Sirene. The polymorphism of purified avenins determined by SDS-PAGE revealed the occurrence of 2 bands around 30 kDa in oat cultivars with relatively high gluten content (12-16 mg kg-1) except for the cultivar Leo while this pattern occurred only in 50% oat cultivars with low gluten content. Quantification of gluten epitopes on purified avenin unit further revealed the three materials (Mojacar, Maris Oberon, SG-K 16370) with the lowest gluten content and presence of one band at 30 kDa. The band pattern at 30 kDa thus represents a promising breeding marker.