Quark-type cheese is a fresh mass cheese with a relatively short shelf life. The aim of this study was to evaluate the in vitro antimicrobial activity of essential oils of basil, marjoram, nutmeg and oregano. The essential oil with better results was added to Traditional Quark Cheese (QT). The antimicrobial activity of essential oils was evaluated through the disk-diffusion assay, determination of the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). To verify the shelf life of QT added with essential oil, microbiological (mold and yeast count, total mesophilic and total coliform) and physical-chemical (acidity, pH, aw, moisture, fat, and color) analyzes were performed during 35 days of storage at 4°C. The acceptability of the product was also evaluated using a 9-point hedonic scale. The essential oil of oregano showed strong antimicrobial activity in the disk-diffusion test against all species of bacteria tested, with inhibition zones between 34.0 and 51.0 mm. The MIC and CMB values also evidenced the greater antimicrobial activity of the oregano essential oil against all tested bacteria, being the chosen one for application in the QT. A lower mold and yeast count (p<0.05) was observed during storage in QT added with oregano essential oil (0.05%), denoting a positive effect in delaying its deterioration. On the other hand, there was no difference (p>0.05) of the QT with oregano oil with control cheese in relation to the count of total mesophiles and total coliforms. For the physicochemical parameters evaluated, there was no significant differences from the control cheese when the essential oil of oregano was added to the QT, thus denoting that the typical physicochemical characteristics of this cheese were maintained. The QT added with oregano essential oil also showed good acceptability (>7), which is a way to preserve the product with a natural ingredient.