- Lightly grease a casserole dish, or you could probably also use a deep dish pie pan. Set aside.
- Take 4 cups of frozen fruit (berries, peaches, a mixture, etc.) and thaw overnight or heat in the microwave for about 6 minutes to thaw.
- Drain off the excess juice for 15 minutes.
- In a medium-size saucepan put 1/2 cup sugar, 3 Table. cornstarch and slowly add the juice leftover from the thawed fruit, stirring nonstop until well combined.
- Turn the heat on to medium-high and cook, stirring, until the liquid boils and the sauce thickens.
- Let the sauce cool for about 10 minutes and then stir it into the thawed fruit. Place the fruit mixture into the greased casserole dish.
- In another mixing bowl put together the topping: 3/4 cup quick oats, 1/3 cup flour, 1/2 cup brown sugar, and 1/2 teaspoons cinnamon. Stir to blend.
- Finely dice 1/3 cup cold butter and add to the oatmeal mixture, using a pastry cutter (or a fork or your fingers) to break up the butter even more until it resembles coarse crumbs.
- Sprinkle the oatmeal mixture over the fruit.
- Bake in a 375 degree oven for 25 minutes.
- Let the fruit crisp cool for 10-15 minutes and then serve with vanilla ice cream.