Blueberry Coffee Cake with Streusel Topping

2 cups flour
1 cup sugar
3 teaspoons baking powder
1 teaspoon salt
1/3 cup softened margarine
1 cup milk
1 egg
1 cup blueberries

Preheat oven to 350 degrees. Beat all ingredients, except blueberries, in a large bowl on a low speed for 30 seconds, then beat on a medium speed for 2 minutes, scraping bowl occasionally.

Grease a 13x9 pan. Spread half the batter in the pan. Sprinkle 1 cup of blueberries over batter, then top with the rest of the batter. Add streusel topping, below, then bake in oven for 40 minutes.

Making the Streusel Topping

1/2 cup walnuts (optional)
1/3 cup brown sugar
1/4 cup flour
1/2 teaspoon cinnamon
3 teaspoons margarine

Mix all ingredients together till crumbly. Sprinkle on top of cake prior to baking.

Glazing the Coffee Cake

Mix 1 cup confectioners' sugar, 2 Tablespoons milk and 1/4 teaspoon vanilla. Drizzle over top of the cake after baking.