Preheat oven to 350°F. Spray an 8 x 4-inch loaf pan with cooking spray and set aside.
In a large bowl, mix together flour, sugar, oat bran, poppy seeds, baking powder and salt.
In a medium bowl, whisk together milk, butter, egg, lemon juice and lemon zest. Add wet ingredients to dry ingredients and mix just until dry ingredients are moistened. Spread batter in prepared pan. Bake for about 40 minutes, or until loaf is light golden brown and a toothpick inserted in center of loaf comes out clean.
Cool loaf in pan on a wire rack for 10 minutes. Remove loaf from pan and cool completely on rack. Cover with plastic wrap and store at room temperature or in the refrigerator.