Preheat the oven to 190°C. Spray a 23 cm glass pie dish with cooking spray.
Combine the peaches, cherries, white sugar and cornflour in a medium saucepan and bring to the boil over a moderate heat. Remove from the heat and stir in the vanilla essence and lemon zest. Spoon into the pie dish.
Combine the oats, brown sugar and flour in a medium bowl. Cut in the butter with a pastry blender or 2 knives until the mixture is crumbly. Scatter over the fruit, place the pie dish on a baking tray and bake for 20 minutes or until the filling is bubbly and the top is browned. Serve warm or at room temperature.