CAKE: In a large mixing bowl, combine butter, milk, eggs, sugar, baking powder, vanilla and flour. Beat until light. Add blueberries and gently stir by hand. Turn into a greased and floured 9 x13-inch pan, spreading coffee cake batter evenly. Sprinkle with crumb topping. Bake at 350 degrees for 35-40 minutes
CRUMB TOPPING: In a medium mixing bowl, combine flour, sugar and cinnamon, stir well. With a pastry cutter or fork, gradually add butter, cutting into the flour mixture until it resembles small peas. Sprinkle topping over coffee cake and bake.