Preheat oven to 400 degrees. In a small bowl, mix together brown sugar, 2 T flour and margarine. Add the oatmeal and vanila, stirring with a fork until well mixed; set aside. In a large bowl combine 1 3/4 c. flour, baking powder, baking soda, sugar and orange rind. In a small bowl combine the orange juice, buttermilik, oil, and egg. Make a well in the cetner of the dry ingredients and add the egg mixture, stirring just until well moistened. Stir in the blueberries. Line the muffin tin with muffin papers. Fill the muffin cups 2/3 full and sprinkle with the crumb mixture. Bake for 20-25 minutes or until the top springs back when touched.