2 29-ounce cans peaches
1/2 cup sugar
1/3 cup cornstarch
1 tablespoon lemon juice
1/3 cup margarine, softened or melted
1 cup quick cooking oats
1/3 cup all-purpose flour
1/2 cup brown sugar
1 teaspoon cinnamon
Preheat the oven to 400°. Open up the peaches and drain the juice into a small saucepan. Arrange the peaches in a lightly oiled 2-quart baking dish. If they are in large pieces then cut them into slices or chunks. Set the peaches aside.
Add the sugar, lemon juice and cornstarch to the drained peach juice. Stir it well with a small whisk or fork. Continue stirring until the cornstarch is dissolved. Heat the mixture over medium-high heat until it boils. You will have to stir it a lot to keep it from sticking and to prevent lumps. The mixture will become very thick as it cooks. When the mixture boils, continue cooking and stirring for a full minute. Remove the mixture from the heat and pour it over the peaches in the dish. Stir the mixture gently so the peaches will be evenly covered with the sauce..
Meanwhile, combine the topping ingredients in a medium bowl. Use a fork to mash them together until they are crumbly. Scatter the topping thickly over the peaches. Bake the crisp at 400° for 30 minutes, or until the topping is lightly browned and the filling is bubbly. Allow the crisp to cool for 20 minutes before serving. This will keep it from burning anyone. Serve with half and half or whipped cream or ice cream