In A Medium Bowl, Stir Together The Flour, Garlic Salt, Pepper, And Oregano. Dredge Chicken In The Mixture To Lightly Coat. Heat Olive Oil And Butter In A Large Skillet Over Medium Heat. Fry The Chicken In The Skillet For 2 Minutes, Or Until Lightly Browned On One Side. Turn Chicken Over, And Add Mushrooms. Cook About 2 Minutes, Until Other Side Of Chicken Is Lightly Browned. Stir Mushrooms So That They Cook Evenly. Pour Marsala Wine Over The Chicken. Cover Skillet, And Reduce Heat To Low; Simmer For 10 Minutes, Or Until Chicken Is No Longer Pink And Juices Run Clear.