Preheat the oven to 375°F. Line an 8x8 or 9x9-inch pan with parchment paper or aluminum foil and spray with non-stick cooking spray.
In a medium bowl, combine the berries and cherries with sugar, cornstarch and lemon juice, and toss to coat. Set aside while you prepare the crumble.
Press a little bit more than half of the crumble into the bottom of your prepared pan, patting it down evenly.
**Optional - adding 1/4 cup chopped pecans, walnuts or sliced almonds to the crust would add a nice crunch if desired