2 cups buttermilk baking mix, such as Bisquick
1/4 cup sugar
2 tbsp. margarine or butter, softened
1 egg
3/4 cup fruit-flavored yogurt (about 8 oz.)
1 tsp. vanilla
Streusel (recipe follows)

Heat oven to 375 degrees. Grease an 8x8x2 inch pan. Mix all ingredients except streusel; beat vigorously 1 minute. Spread in pan; sprinkle with streusel. Bake 30 to 35 minutes or until wooden pick inserted in center comes out clean. Cool 10 minutes; cut into squares. Makes 9 servings.
Streusel: Mix 1/4 cup buttermilk baking mix, 1/4 cup sugar and 2 tbsp. firm margarine or butter until crumbly. Stir in 1 tbsp. grated lemon or orange peel, if desired.