Preheat oven to 375 degrees F. Coat twelve 2-1/2-inch muffin cups with nonstick spray or line with paper baking cups; set aside.
In a large bowl combine all-purpose and whole-wheat flour, oats, baking powder, cinnamon, and salt. In a medium bowl combine egg, milk, sugar, and oil. Add egg mixture all at once to flour mixture; stir just until combined. Fold in the cranberries and toasted walnuts. Spoon into prepared muffin cups.
Bake for 15 to 18 minutes or until tops are lightly browned and a toothpick inserted in centers comes out clean. Cool muffins in pans for 5 minutes. Remove muffins from pans. Serve warm. Makes 12 muffins.