Preheat oven to 425 degrees F (220 degrees C). Lightly grease two baking sheets.
In a large bowl, stir together whole wheat flour, white flour, rolled oats, baking soda and salt. Gently mix in the buttermilk until a soft dough is formed. Knead very lightly. Divide dough into 4 pieces; form into rounded flat loaves. Mark each loaf with an 'X' and place on prepared baking sheets.
Bake in preheated oven until golden brown, about 30 to 45 minutes.