STREUSEL TOPPING:

1/2 cup packed brown sugar
1/2 cup oats
2 teaspoons cinnamon
1/4 cup butter, chilled

Combine first 3 ingredients in small bowl. Cut in 1/4 cup chilled butter using fingers or pastry blender until mixture resembles coarse meal. Set aside.

CAKE:

3 cups flour
1-1/2 teaspoons baking powder
1-1/2 teaspoons baking soda
3/4 cup unsalted butter, softened
1-1/3 cups sugar
3 large eggs
1 teaspoon vanilla extract
1-1/2 cups plain nonfat yogurt
1 medium Granny Smith apple, peeled and chopped

Preheat oven to 350°F.

Grease two 9x5x3 inch loaf pans.

Sift flour, baking powder and baking soda into large bowl. Using electric mixer, cream 3/4 cup butter and 1-1/3 cups sugar together in another large bowl until fluffy. Add eggs, 1 at a time, beating well after each addition. Mix in vanilla.

Fold in dry ingredients alternately with plain yogurt, beginning and ending with dry ingredients.

Pour about 1-1/2 cups batter into bottom of each prepared pan. Sprinkle 1/3 cup streusel over each. Sprinkle 1/4 of apple over each.

Divide remaining batter, streusel and apple between pans, beginning with batter. Run small knife through batter to create swirl.

Bake in a 350°F oven until golden brown and toothpick inserted into centers comes out clean, about 55 minutes. Cool on racks. Serve warm or at room temperature.