Preheat oven to 350 degrees. Grease and flour an 8 1/2-by-3 5/8-by-2 5/8-inch loaf pan.
Pour vinegar into 1-cup glass measure. Add non-fat milk to measure 1 cup total. Let stand 10 minutes to sour.
Combine organic flour, brown sugar, baking powder, baking soda and salt. Stir in oats, plums and walnuts.
Beat egg in bowl. Add soured milk and oil. Pour all at once into dry ingredients. Stir just until evenly moistened. Turn into pan.
Bake for 45 minutes or until wooden pick inserted in center comes out clean. Remove bread from pan to wire rack to cool. Store overnight for easier slicing. Makes one loaf.