Combine first 3 ingredients in a medium bowl; cut in margarine with a pastry blender until mixture resembles coarse meal.
Combine buttermilk and remaining 3 ingredients in a medium bowl, stirring well with a wire whisk. Add buttermilk mixture to flour mixture, stirring just until dry ingredients are moistened.
Turn dough out onto a lightly floured surface, and knead lightly for 30 seconds. Divide dough in half, and pat each half into a 3/4-inch-thick circle. Cut each circle into 6 wedges. Place wedges on an ungreased baking sheet. Bake at 400° for 15 to 18 minutes or until lightly browned. Serve warm.
Tip: Brown sugar helps make these scones tender as well as sweet. Even with real sugar, each wedge has only 16 grams of carbohydrate.