Preheat oven to 375° F (190° C). In shallow 20 x 20-cm baking dish, arrange blueberries; set aside.
In medium bowl, combine flour, brown sugar, oats and cinnamon. Stir in Hellmann's® Real Mayonnaise. Using fingers, gently squeeze dough to form crumbs. Evenly sprinkle crumbs over blueberries. Bake 30 minutes or until topping is golden.