Combine the raisins and Marsala in a small saucepan, bring to a boil and then remove from the heat to let the raisins plump up with the wine. Remove the peppers' seeds and ribs; slice lengthwise into strips. Peel and quarter the onions. Saute the peppers and onions in the oil until tender but not limp. Stir in the raisins and serve warm or at room temperature. Serves four.