In order to investigate the effects of Plant Growth Promoting Rhizobacteria (PGPRs) inoculation on the growth, yield and quality of eesetial oils of Summer savory (Satureja hortensis L .) a pot experiment based on randomized complete block design with three replication were conducted in field of Research Institute of Forests and Rangelands at 2012. Bacterial treatments include suspension of three species of rhizobacteria namely Azotobacter, Azospirillum, Pseudomonas suspension in single and combination application of these bacteria include Azotobacter- Azospirillum, Azotobacter –Pseudomonas, Azospirillum-Pseudomonas, Azotobacter- Azosperillium-Pseudomonas and control (without inoculation of any bacteria), which applied as root inoculation on summer savory plants. Results revealed that inoculation of plants with plant growth promoting rhizobacteria had significant effect on all of assessed parameters such as vegetative growth criteria and essential oil yield and quality. The highest value for traits such as plant height (45.67 cm), canopy diameter (40.54 cm), dry weight of shoot( 33.82 g/p), aerial part yield(3578 kg/ha), leaf yield (451 kg/ha), inflorescence yield(1398 kg/ha), essential oil weight percentage(2.33 %) essential oil efficiency (2.43 %) and essential oil yield (76.8 %) were obtained by application of Azotobacter- Azosperillium-Pseudomonas combination and the lowest amount for all of mentioned traits were achieved in control treatment. The highest amount for α-terpinene( 53 mg/l) thymole (48.5 mg/l) were obtained by inoculation ith Azotobacter –Pseudomonas combination and Azotobacter respectively. Results of this experiment indicated that inoculation of summer savory plants with combination of three assessed plant growth promoting rhizobacteria leads to the highest indices for plant dry weight and essential oil yield. In general Inoculation of summer savory plants by plant growth promoting rhizobacteria enhancing root growth and development supplying favorable condition for plant growth with respect to supplying better condition for water and nutritional elements absorption from soils.