• Preheat the oven to 350°F, and lightly grease a 2 ½-quart baking dish.

To Make the Topping

• In a medium bowl, combine the oats, cold butter, flour, brown sugar, granulated sugar, and cinnamon. Use a pastry cutter, forks, or your hands to make sure the ingredients are well mixed. There shouldn’t be any dry, sandy patches left in the bowl.
  1 cup old fashioned oats, ½ cup all-purpose flour, ½ cup unsalted butter, ½ cup light brown sugar, ¼ cup granulated sugar, ½ teaspoon ground cinnamon

To Make the Filling

• Place the thawed berries, sugar, cornstarch, lemon juice, lemon zest, and cinnamon into a large bowl and toss to combine.
  32 ounces frozen berries, ½ cup granulated sugar, ⅓ cup cornstarch, 1 large lemon, ½ teaspoon ground cinnamon
• Transfer the berry mixture to the prepared dish then top with the crisp topping.
• Bake for 25-30 minutes or until the oat topping is golden brown and crunchy and the filling is bubbly.
• Let the crisp cool for 10-15 minutes before serving.
• Scroll up and see the post for tips, FAQs, and storage recommendations.