Preheat the oven to 350 F. Stir together the grapes, pear, sugar, flour, and cinnamon in a medium bowl. Spoon into four lightly buttered 2-cup baking dishes; set aside.

To prepare the topping: Toast the oats in a small skillet over medium heat for 3 to 4 minutes, or until lightly browned, stirring frequently. Let them cool, then mix them in a medium bowl with the flour, butter, sugar, and cinnamon. Stir with a fork until the mixture is crumbly, then stir in the walnuts. Sprinkle over the fruit and bake for 35 to 40 minutes, or until the grapes are soft, tenting the cups with foil if the topping browns too quickly.