Place rack in center of oven, and heat oven to 325 degrees. Lightly brush a 9-by-12 1/2-inch baking pan with canola oil, dust with flour, and tap to remove excess. Set aside.
In a large mixing bowl whisk together egg, milk, canola oil, and vanilla for 2 minutes on medium speed. Add 1 1/2 cups flour, granulated sugar, baking powder, and salt; continue mixing for 2 minutes.
Spread batter evenly into prepared pan, and set aside. In a medium bowl, combine remaining 2 1/2 cups flour, brown sugar, and cinnamon. Pour melted butter over flour mixture, and toss with a rubber spatula until large crumbs form. Sprinkle crumbs over batter.
Place pan in oven, and bake, rotating pan after 10 minutes. Continue baking until a cake tester comes out clean, about 10-15 minutes more.
Transfer baking pan to a wire rack to cool.Using a serrated knife or bench scraper, cut into 3-inch squares. Store in an airtight container for up to 3 days.