Cut the broccoli into florets, and steam, covered, for 3 minutes or until crisp-tender. Spoon into a serving bowl, and keep warm. Melt the margarine in a small, heavy saucepan over medium-heat. Stir in the flour, and cook 1 minute, stirring constantly. Combine the orange rind and juice. Gradually add orange juice mixture to flour mixture, and cook until mixture is thcik and bubbly, stirring constantly. Pour sauce over broccoli.