Although I haven't tried doing this you could probably use a whole cake mix, double the rest of ingredients and bake in a 13x9x2 pan.  Just watch the baking time.  For a quick dessert serve slightly warm with a scoop of vanilla icecream

½ pkg. spice cake mix
1 egg
½ cup vegetable oil
1 cup quick cooking oatmeal
½ cup raisins
½ cup chopped nuts
½ cup plain yogurt

Directions:

Preheat oven to 375 degrees.  Combine all ingredients in a large bowl. Mix well until cake mix is moist. Grease an 8 inch square baking pan. Pour mixture into pan and bake  for about 20 minutes. Remove from oven when center is done.  Cool and cut into bars.