Preheat the oven to 350\u00b0F. Spray an 11\u00d77-inch baking dish with cooking spray and set aside. Remove the stems from the strawberries. Prepare them by leaving small ones whole, cut medium ones in half, and quarter large ones. Place the strawberries in a large bowl. Toss them until coated in the cornstarch, sugar, lemon juice, and vanilla. Set aside. In a medium-sized bowl, stir together the oats, flour, brown sugar, melted butter, and cinnamon until combined and crumbly.<\/p>\n
Give the strawberries another good stir and place them in the baking dish in an even layer. Take your hands and add the crumble on top, breaking it up and crumbling it evenly all over.<\/p>\n
Bake for 30-40 minutes until the strawberry mixture is bubbling up along the sides of the baking dish, and the crumble is golden brown.<\/p>\n
Allow the crumble to sit for 10 minutes before serving (this will give the filling time to thicken.)<\/p>\n