Blueberry Coffeecake

2 c flour
1 c sugar
3 t baking powder
1 t salt
1/3 c margarine softened
1c milk
1 egg
1 c blueberries
Preheat oven to 350. Beat all ingredients, except blueberries, in a large bowl on a low speed for 30 seconds. Then beat on a medium speed for 2 min, scraping bowl occasionally. Great a 13x9 pan. Spread half the batter in the pan. Sprinkle one cup of blueberries over batter, then top with the rest of batter. Add streusel topping below, then bake in oven for 40 min.
Streusel:
1/2 c walnuts, chopped
1/3 c br sugar
1/4 c flour
1/2 t cinnamon
3 t margarine
mix together until crumbly. Sprinkle on top of cake.
Glaze:
1 c powdered sugar
2 T milk
1/4 t vanilla
combine, drizzle over top of coffeecake.