Heat oven to 350°F. Place paper baking cup in each of 24 regular-size muffin cups.
In large bowl, beat butter and sugar with electric mixer on medium speed until light and fluffy. Add egg and banana, beating until well mixed. Beat in yogurt. Stir in oats, dried strawberries and walnuts. Divide mixture evenly among muffin cups.
Bake about 25 minutes or until tops are golden brown. Cool on rack 15 minutes.