Crush crackers in a blender or with a rolling pin and transfer to a pie plate. Melt margarine and stir into cracker crumbs, pressing mixture evenly over bottom and up sides of the pan. In medium mixing bowl, combine sugar, egg whites, vanilla and lemon juice; beat at medium speed for 15 minutes or until mixture is stiff. Fold in whipped topping and peaches. Pile lightly into prepared crumb shell. Chill for 1.5 hours and serve. NUTRITION PER SERVING: 227 calories 71% carbohydrate 4% protein 25% fat