In a medium saucepan, combine cranberries, granulated sugar, lemon juice, and cornstarch. Cook over medium heat until the cranberries burst and the mixture thickens, about 10 minutes.

Remove from heat and let it cool slightly.

Preheat the oven to 350°F (175°C).

In a mixing bowl, combine flour, rolled oats, brown sugar, melted butter, and salt. Mix until crumbly.

Press half of the crumble mixture into the bottom of a greased 9x9 inch baking pan.

Spread the cranberry filling evenly over the pressed crumble base.

Sprinkle the remaining crumble mixture over the cranberry filling.

Bake in the preheated oven for 25-30 minutes or until the top is golden brown.

Allow to cool completely before cutting into bars.