The chemical composition of the essential oils obtained from the species restricted to Greece and the eastern Mediterranean region, Satureja spinosa L. and Thymus longicaulis L.; species endemic to central and south Greece, Satureja parnassica ssp. parnassica Heldr. and Sart ex Boiss.; species endemic to the island of Crete, Origanum dictamnus L.; and species widely distributed in the Mediterranean region, Satureja thymbra L. and Origanum vulgare L. subsp. hirtum, were determined by gas chromatography (GC) and GC/mass spectrometry (MS) analysis. The in vitro antibacterial activities of the essential oils were evaluated against a panel of five foodborne bacteria (Escherichia coli 0157:H7 NCTC 12900, Salmonella enteritidis PT4, Staphylococcus aureus ATCC 6538, Listeria monocytogenes ScottA, and Bacillus cereus FSS 134). The analytical data indicated that various monoterpene hydrocarbons and phenolic monoterpenes constitute the major components of the oils, but their concentrations varied greatly among the oils examined. The antibacterial assay results showed that 5 muL doses of the essential oils extracted from the endemic Satureja species in Greece possess remarkable bactericidal properties, which are clearly superior as compared to those of Origanum and Thymus species essential oils. Therefore, they represent an inexpensive source of natural mixtures of antibacterial compounds that exhibit potentials for use in food systems to prevent the growth of foodborne bacteria and extend the shelf life of the processed food.