Proof 1 tablespoon yeast in 3/4 cup warm water with 1 teaspoon sugar for 8-10 minutes or until foamy.
In the stainless steel mixing bowl add in 2 cups EACH white and whole wheat bread flour and the rolled oats; mix slightly to combine with a spoon.
In the microwave warm the buttermilk, butter, 3 tablespoons sugar and 1-1/2 teaspoons salt for about 40 seconds until warm (the butter does not have to melt completely) then pour into the stainless steel mixing bowl with the flour.
After the yeast is proofed, add into the bowl along with the 1/2 teaspoon baking soda and start mixing/kneading adding in more WHITE flour as needed to create a soft semi-sticky dough (because of the oatmeal and whole wheat flour the dough will be more sticky than usual).
Knead for 10 minutes.
Remove the dough to a lightly-floured surface; cover with a clean tea towel and let rest for 10 minutes.
Gather up the dough and knead gently for about 15 seconds with your hands (it will come together nicely).
Generously grease a large bowl with oil.
Place the dough in the bowl, cover with plastic wrap or a clean tea towel and let rise for about 1 hour and 15 minutes (it might take more or less time depending on the temperature of your kitchen, or place in a warmed oven to rise).
Remove and punch down dough.
Place on a floured surface and roll out to about 14x8 inches (does not have to be exact size!).
Roll up tightly and tuck the sides under to fit the 8x4-inch loaf pan (I just slice off the ends of the dough enough to fit into the pan and pinch the dough together, it makes for a more even loaf).
Cover and let rise for about 30-45 minutes (depending on how warm your kitchen is) in a warm place covered with a clean tea towel.