In this study, the chemical composition and antimicrobial activities of the essential oil of the Rhinanthus angustifolius subsp. grandiflorus plant were investigated. Essential oil was obtained from all parts of the plant by hydrodistillation and was analyzed by GC-FID and GC-MS. 31 components representing 99.46% of the total oils were characterized. The main components of these species were found to be 2,3-dihydro-5-methyl-1H-indene (25.14%), alpha-cubebene (19.27%), 1-hexadecene (15.59%) and hexadecanoic acid (12.14%). The antimicrobial activity of the isolated essential oil was investigated. Antimicrobial activity was observed against B. cereus, E. coli, E. coli O157:H7 and S. Aureus microorganisms. Moreover, an effect on the ferments of B. cereus, E. coli, E. coli O157:H7 and S. Aureus was detected.