01 - Preheat oven to 350°F. Lightly grease a 9-inch square or oval baking dish with butter or nonstick spray.
02 - In a large bowl, gently toss the mixed berries with granulated sugar, cornstarch, vanilla extract, lemon juice, and a pinch of salt until evenly coated. Spread the berry mixture in an even layer across the bottom of the prepared baking dish.
03 - In a separate mixing bowl, combine the rolled oats, all-purpose flour, shredded coconut, packed brown sugar, ground cinnamon, and salt. Add the cold butter cubes and vanilla extract. Using your fingers or a pastry cutter, cut the butter into the dry ingredients until the mixture forms coarse, pea-sized crumbs.
04 - Sprinkle the crisp topping evenly over the berry filling, covering the surface completely.
05 - Bake on the center rack for 35 minutes, or until the topping is golden brown and the berry juices are bubbling around the edges.
06 - Remove from the oven and allow to cool for at least 10 minutes before serving. Serve warm, optionally accompanied by vanilla ice cream or freshly whipped cream.