The effect two drying treatments (solar and oven), three blanching treatments (no blanching, water and steam), and four chemical treatments (no chemical, lemon juice, vinegar and potassium bisulfite) on oyster mushroom quality was investigated. Sensory quality, total phenolics, total flavonoids, ergothioneine, oxygen radical absorbance capacity, moisture, mold infestation, mineral content and protein were evaluated. Among the un-blanched samples, those that were treated with lemon juice and those without any chemical pretreatment before drying had better appearance, flavor and were more generally acceptable than those with vinegar and potassium bisulfite treatments. However, when blanching was done, samples treated with potassium bisulfite had superior sensory quality when compared to lemon juice, vinegar and the control. Solar drying caused more browning when compared to oven drying. The combination of water blanching with either lemon juice or vinegar treatments before drying resulted in higher flavonoid content. Lower ergothioneine and total phenolic compounds were observed in blanched mushrooms compared to the un-blanched ones. Total flavonoids were highest in the water blanched samples and least in the un-blanched ones. Among the chemical pretreatments, higher total phenolic compounds were observed in vinegar and potassium bisulfite treated samples. Blanching resulted in lower K, Mg, Na, S and P content when compared to the control. Mineral nutrients varied with chemical pre-treatments. Blanching followed by either lemon juice or no chemical treatment resulted in high mold infestation. Among the un-blanched samples, those treated with vinegar had the least mold infestation. Drying method, blanching, and chemical pretreatments affected oyster mushroom quality hence a need to carefully select preservation methods so as to minimize quality compromise.