- Preheat oven to 325 degrees F. Lightly grease a loaf pan. In a large mixing bowl, cream together butter and sugar. Add eggs; beat well. Stir in peanut butter, bananas, flour and baking soda until blended. Fold in walnuts. Pour into prepared pan. Bake at 325 degrees F for 30 minutes. Remove to a wire rack to cool. Cut into pieces and serve.