Preheat an oven to 375° degrees. Lightly butter or spray a 9x6-inch baker or an 8x8-inch baking dish.
In a medium size mixing bowl, toss the blueberries in the sugar, cornstarch, lemon juice and lemon zest. Pour into the prepared dish and set aside.
In a medium size mixing bowl, whisk together the flour, oats, brown sugar, salt and cinnamon. Using a pastry blender, cut in the butter until pea size (or slightly larger) form. Sprinkle over the blueberries.
Place in the oven and bake for 30-35 minutes or until the juices bubble and the top is golden brown.
Remove form the oven and allow to cool for 10-15 minutes before serving.
Notes
*If you prefer your crisp on the sweeter side, add up to 2 additional tablespoons of sugar.