In a large bowl, combine flour, sugar, baking powder and salt. Cut in butter until mixture resembles coarse crumbs. Stir in walnuts.
In a small bowl, beat eggs, milk and vanilla; stir into dry ingredients just until moistened. Gently fold in blueberries.
Pour into two 9-in. x 5-in.x 3-in. loaf pans. Bake at 350 degrees F or 175 degrees C for 50-60 minutes or until bread tests done.
Cool in pan 10 minutes before removing to a wire rack.