In a large bowl, combine berries, sugar, flour, lemon juice and lemon zest. Stir until berries are coated and set aside.
In a separate bowl, whisk together rolled oats, flour, brown sugar, granulated sugar, cinnamon and salt. Add butter and use a pastry cutter (or two forks) to cut the butter into the dry ingredients until the mixture resembles coarse sand.
Pour berries into prepared baking dish. Evenly sprinkle crisp mixture on top.
Bake berry crisp at 375° F for 30 to 40 minutes or until the top is golden brown and the berries are bubbling. Serve warm with a scoop of vanilla ice cream.
Frozen berries may be used in place of fresh berries. Use high quality frozen berries for the best flavor and increase flour to 3 tablespoons to act as a thickener.Store triple berry crisp covered in the refrigerator for up to 3 days.Reheat triple berry crisp in a 350° F oven for 10 minutes or until heated through.Freeze triple berry crisp once it has completely cooled. Wrap the dish twice in aluminum foil to prevent freezer burn. Crisp will keep frozen for up to 1 month. Reheat at 350° F for 20 minutes or until heated through.Recommended tools: kitchen scale, mixing bowls, pastry cutter, 2-quart baking dish