Preheat the oven to 400 and lightly oil a large baking sheet. Sprinkle the sheet with cornmeal, semolina, or oats, and set aside.
Put the 1/2 cup oats in mixing bowl. Stir in the buttermilk, molasses and oil; reserve.
Mix dry ingredients in large bowl. Make a well in the dry mixture and add the liquid all at once; add raisins. Stir briskly with a wooden spoon until dough pulls together in a shaggy mass. Let rest 3 minutes.
Flour your work surface and hands. Scoop half of the dough onto floured surface and knead gently; if dough is a little sticky, a dough scraper might help. Knead for 1 minute, shaping into a ball. Place on the baking sheet. Using a sharp, serrated knife, make two parallel slashes on the surface of the dough, about 3/4 -inch deep. Repeat for the other half of dough and place on sheet; leave plenty of room between the loaves.
Bake for 20 minutes, then reduce the heat to 375 and bake 20 minutes more, until dark and crusty. When done, the bottom should sound hollow when tapped with a finger. Cool loaves before slicing.