Heat oven to 325 degrees.
Lightly brush a 9x12 ½ in. baking ban with canola oil, dust w/ flour.
In medium bowl, sift together 1 ½ cups flour, granulated sugar, baking powder, and salt.
In second bowl, whisk egg, milk, canola oil, and vanilla.
Fold dry ingredients into egg. Spread batter evenly into pan.
In a medium bowl, combine remaining 2 ½ cups flour, brown sugar, and cinnamon. Pour melted butter over flour mixture, and toss until large crumbs form.
Sprinkle crumbs over batter, and bake, rotating pan after 10 min. Continue baking until a cake tester comes out clean, and then 10 min. more.