In this research, considering the importance of medicinal plants in the food and pharmaceutical industries and the undeniable role of the drying process in their processing, a solar-vacuum drying system was implemented and evaluated for drying medicinal plants. The system includes a drying chamber, a cold water chamber, a vacuum pump, temperature sensors, pressure gauges, an Arduino control board, a water pump, a condenser, and control valves. To evaluate the dryer and drying kinetics, experiments were conducted on oregano products at a pressure of 30 kPa in the solar-vacuum dryer and drying under sunlight, shade, and oven. The results of the drying kinetics study showed that the minimum and maximum drying times were 188 minutes for the dryer and 1620 minutes for the shade, respectively. The drying kinetics in the developed dryer were modeled. The modified Henderson and Pabis model with an R^2 value greater than 0.96 and an RMSE value less than 0.05 was selected as the best-performing model. GC-MS was used to evaluate the quality of the dried essential oil in various experiments. The main compounds, eucalyptol and borneol, had the highest values. The highest amount of eucalyptol was obtained for the solar treatment at 30.908%, and the highest amount of borneol was associated with the shade treatment at 24.698%.