In a large bowl, cream butter and sugar until light and fluffy. Beat in eggs and vanilla until blended. Combine the flour, baking powder and salt; add to creamed mixture alternately with milk, beating well after each addition. Fold in blueberries.
Pour into a greased 13-in. x 9-in. baking dish. For topping, combine sugar and cinnamon. Cut in butter until mixture resembles coarse crumbs. Sprinkle over batter.
Bake at 375° for 35-40 minutes or until a toothpick inserted near the comes out clean. Cool on a wire rack. Yield: 12-16 servings.