Preheat your oven to 350°F (175°C). Line an 8x8 inch baking dish with parchment paper, letting some hang over the edges for easy removal later.

In a bowl, gently mix together the diced rhubarb, sliced strawberries, sugar, cornstarch, vanilla extract, and salt. Set it aside to allow the flavors to mingle while you prepare the crust.

In another bowl, combine the flour, rolled oats, brown sugar, and melted butter until the mixture is crumbly.

Press half of the crumbly mixture into the bottom of the prepared baking dish, creating a layer for the filling.

Spoon the fruit mixture evenly over the crust. Top it with the remaining crumb mixture, spreading it out evenly.

Bake in the preheated oven for about 30-35 minutes, or until the top is golden and the filling is bubbly.

Allow the bars to cool completely in the dish before lifting them out using the parchment paper edges and cut them into squares.

Enjoy them on their own, or add a scoop of ice cream on top for a delightful twist!