Heat Oil In A Large Skillet Over Medium High Heat. Saute Mushrooms, Bell Pepper And Onion Until Soft; Remove From Skillet And Set Aside. Saute Chicken For About 15 Minutes, Or Until Cooked Through And Juices Run Clear. Return Mushroom Mixture To Skillet And Stir All Together. Bring A Large Pot Of Lightly Salted Water To A Boil. Add Pasta And Cook For 8 To 10 Minutes Or Until Al Dente; Drain. Return Pasta To Pot Over Medium Heat And Stir In Spaghetti Sauce; Heat Through, Then Stir In Chicken Mixture And Heat Through, Stirring. Serve Hot.