• Preheat the oven to 350F (180C). Lightly grease a 9x13 inch (23x33 cm) baking pan or line with parchment paper, leaving an overhang around the edges.

Fruit Filling Layer

• In a large bowl, toss together the sliced strawberries, rhubarb, sugar, cornstarch, and lemon juice so that the fruit is evenly coated. Set aside.

Oatmeal Crumble Layer

• In a very large bowl, whisk together the flour, brown sugar, white sugar, cinnamon, salt and oats until you no longer see clumps of brown sugar and the mixture is even.
• Stir in the melted butter. The mixture should be slightly crumbly and dry.

Assembling & Baking the Bars

• Press a little over ½ of the oatmeal crumble layer into the bottom of the prepared pan to form an even layer.
• Spoon the fruit mixture overtop so that it evenly covers the oatmeal base. If there is a lot of juice in your bowl, you don't need to add it to the pan.
• Crumble the remaining oatmeal crumble mixture over top of the fruit layer.
• Bake in the preheated oven for about 40-50 minutes, or until the top looks golden and you can see the fruit juices gentling bubbling through.
• Cool the bars completely before slicing.
• If you lined the pan with parchment, optionally lift the bars out of the pan using the overhang of the parchment paper (I always hold onto the long edges for easier lifting). Place on a cutting board and slice. If you greased the pan, slice the bars in the pan.