Preheat an oven to 350 degrees. Grease a 9x9 square pan.
For the fruit filling:
Gently mix together the cut fruit, sugar, and corn starch. Pour the fruit filling into a greased pan and set aside.
For the crisp topping:
Using a food processor or blender, pulse 1 cup of oats to make oat flour. This may take 1-3 minutes of processing time to achieve.
In a seperate bowl, mix together the oat flour, whole oats, sugar, vanilla, salt, and butter. The mixture will be crumbly like a wet sand.
Using your hands, crumble the topping onto the fruit filling. Squeeze the crisp mixture together to make some chunkier bites before dropping them on top.
Cook the crisp uncovered in 350 degree oven for about 40 minutes. If the crisp becomes too brown, loosely cover with foil for the last few minutes of baking. The crisp is done when the middle of the pan is bubbly and the topping is brown.