Preheat the oven to 375°F. Spray an 8x8-inch baking dish with non-stick cooking spray.

In a medium pot over medium-high heat, stir together the cherries, water, sugar, and cornstarch. Bring to a simmer then reduce the heat to low. Continue cooking for 10 minutes, stirring frequently, until the mixture thickens. Transfer to the prepared baking dish and set aside.

In a medium bowl, combine the flour, brown sugar, cinnamon, oats, and pecans. Add the cubed butter to the bowl. Using your fingers or a pastry cutter, work the butter into the flour mixture until it resembles coarse crumbs. The mixture should have a crumbly texture with pea-sized lumps of butter throughout. Sprinkle the topping over the cherry mixture.

Bake, uncovered for 25 minutes, then lightly cover with foil to prevent excess browning and continue baking for an additional 15 minutes. (Total baking time = 40 minutes.)

Cool until the filling stops bubbling and serve warm.