• The 437 volatile organic compounds, of which 414 were shared metabolites in the three Triticeae crops, with 3 metabolites unique to oats. • The 307 differentially accumulated metabolites from all the comparison groups. • Terpenoids and esters are the key metabolites determining the differences in flavor. • The alpha-linolenic acid and phenylalanine pathways are the most significant metabolic pathways. • The 42 differentially accumulated metabolites may be leading to the flavor differences.