Preheat the oven to 190 degrees C. Grease a baking tray or line with baking paper.
In a large bowl rub the margarine into the flour until the mixture resembles fine breadcrumbs. Add the salt, baking powder and then the oats. Add enough cold water to bind the dough, but do not add so much as to make it sticky.
Turn the oatcake dough out onto a floured surface and roll out. Cut into discs and place on the prepared baking tray.
Bake for 15 to 20 minutes until firm.
Oatcakes are best made with medium oatmeal, which refers to the grade of oats ranging from very fine through to the rougher coarser variety.
Traditional Scottish oatcakes are usually made with lard or dripping for extra flavour. Feel free to substitute with the margarine for a richer flavour and texture.