Preheat oven to 375F. Coat the bottom and sides of a 9x13 glass pan with non-stick cooking spray. Then gently mix peaches, blueberries, lemon juice, lemon zest, and cornstarch in large bowl.

In a medium-sized bowl, add rolled oats, flour, sugar, and sea salt. Cut in cold butter with pastry cutter or mix with your hands. The mixture should be lumpy and crumbly, hence a crumble.

Pour peach mixture into greased pan and spread evenly. Then cover fruit mixture with prepared crumble.

Bake for 45-50 min or until the top is slightly browned and the juices from the fruit are bubbling. Allow to cool for 15 minutes before serving. Serve alone or top with vanilla ice cream or freshly whipped cream. Refrigerate leftovers.