Beat egg whites with baking powder, salt and cream of tartar until nearly stiff. Add sugar, gradually, beating until very stiff, but not dry. Combine oats and walnuts and blend into egg whites mix. Fold in vanilla. Spoon into 9" pie plate, making the meringue thick around the edges, leaving a depression in the center for filling. Bake at 325~F for 25 minutes, or until lightly browned. Cool. Drain raspberries and place juice in small saucepan. Carefully blend in cornstarch and cook over medium heat until juice is thickened. Cool slightly and then blend into berries.Spoon into cooled meringue shell. Cover with whipped cream and garnish with coconut. Refrigerate several hours before serving.