Technical Abstract: This research studied the processing performance and product quality of Thompson seedless grapes dried using microwave-assisted convective hot air drying as well as the effect of blanching and dipping pretreatments. Two pretreatment methods were compared, dipping into 2% ethyl oleate (V/V) and 5% potassium carbonate solution (m/V) at 40 degrees C for 3 minutes and steam blanching at 90 degrees C for 140 s, to accelerate drying rate and inactivate PPO aiming to improve drying rate and product color. Pretreated grapes were dried in a microwave-assisted convective dryer at 0.25 W/g specific power and 60 degrees C air temperature. In this study, dielectric and physical properties of grapes were calculated using descriptive equations for fruits and vegetables. Semi-theoeretical models were used to describe the drying curves of both pretreated and untreated grapes. A center and near surface temperature profile of grapes was obtained using fiber optic probes. Experimental center temperature was modeled using one dimensional heat equation and was simulated using a Partial Differential Equation toolbox of Matlab. The results showed that the maximum difference between experimental and predicted values were 4 degrees C which occurred at the initial heating up period. It has been observed that dipping into a solution had no effect on the drying rate whereas steam blanching significantly reduced the drying time and produced a product with a desirable color.