Preheat oven to 350F/180C. Use a 14”x6” tart pan with removable bottom, or you can use a regular tart pan and line it with parchment paper.
In a bowl, add the crust ingredients and mix well using your hand. Transfer to the tart pan, press and spread evenly.
Place the strawberries on a paper towel to absorb some of its juices. Distribute the strawberries and blueberries on the crust, keep aside.
In a bowl, add the streusel ingredients and mix well. Take some of the mixture and press it in your hand, take a small piece from it (around 1 ½ inch) and place over the berries, keep doing so until you almost cover the berries with the streusel. The streusel should look like small lumps.
Bake on the middle shelf for 25 to 27 minutes or until the top is golden in color.
Cool while in the pan for 10 minutes, remove from pan and place on cooling rack. Cut into bars.