1. Adjust oven racks to center and lower thirds of oven. Place a large sheet of foil on lower rack. Heat oven to 375 degree F. Butter a shallow 2-quart baking dish.
2. For the filling, combine berries, granulated sugar and lemon peel in large bowl. Stir lemon juice and cornstarch in cup until smooth. Gently stir cornstarch into berry mixture, just until blended. Spoon filling into prepared dish.
3. For the topping, combine oats, hazelnuts, brown sugar, flour and cinnamon in medium bowl. With pastry blender or 2 knives, cut in butter until mixture is crumbly and begins to stick together slightly. Sprinkle topping evenly over berries. Bake on center oven rack until filling begins to bubble around sides and is hot in center, 60 to 65 minutes. (If topping browns too quickly, cover loosely with foil during last 15 minutes or baking.)
4. Cool crumble completely on wire rack. Hot filling will be loose, but will firm as it cools. Serve with vanilla ice cream. Makes 8 servings.