Combine all filling ingredients in a large bowl. Stir till all fruit is coated, and cornstarch is dissolved. Pour into a greased 8″ pan or casserole dish.
Combine flour, salt, oats, and brown sugar in a mixing bowl. Stir together, then add butter. Mix with your hands till butter is incorporated evenly. Spread topping ingredients over fruit.
Bake at 375° for 35-40 minutes or till fruit is bubbly and topping is light brown and crispy.
Let cool for 15-20 minutes before serving. (Fruit will set up as it cools.)
Serve warm with vanilla ice cream.
Notes
This crisp is juicy. If you want a thicker filling, you can add another tablespoon or two of cornstarch.
You can double the recipe and bake it in a 9x13" pan. Bake for about 45 minutes.