1 c. all-purpose flour
1/3 c. quick-cooking rolled oats
1/2 c. sugar
2 tbsp. milk
1/2 tsp. finely shredded lemon peel
1/2 c. whole wheat flour
1 tsp. baking soda
1/2 c. butter
2 eggs
1 tsp. vanilla

Can use 1 cup:

Finely shredded zucchini
Carrots
Or peeled pears or pumpkin
Or finely chopped peeled peaches

Combine flours, oats, and soda; set aside. In a large mixer bowl beat butter with an electric mixer on medium sped for 30 seconds. Add sugar; beat until fluffy, scraping sides of bowl often. Add eggs, milk, vanilla, and lemon peel; beat well. Stir in vegetable or fruit. Add flour mixture, a THIRD at a time, beating on low speed until combined. Stir in walnuts.