- To prepare this dish ahead, cook the orzo pasta as directed. Drain well; toss with 1/2 teaspoon oil. Spoon into resealable plastic food storage bag and refrigerate for up to 1 day. Just before serving, cook butter, onion, rosemary, nuts, dried raisin and cherry mixture and salt. Meanwhile, warm the orzo in the microwave or in a saucepan; stir in onion mixture.