Grease the bottom and sides of a 9x13-inch baking pan. Line with parchment paper so the paper overhangs the long sides of the pan.
In a large mixing bowl, whisk together the gluten free flour blend, salt, baking powder, baking soda, and cinnamon.
Add the melted butter, sugars, eggs, vanilla, and rolled oats. Stir until combined.
Fold in 1 cup of chocolate chips.
Transfer the cookie dough to the prepared pan and spread evenly around the pan.
Sprinkle the remaining chocolate chips over the top of the cookie dough.
Bake cookie bars for 25-30 minutes or until the top of the bars is golden brown.
Place the baked bars on a wire rack and allow to cool completely before cutting into squares.
Notes
After greasing the pan, line it with enough parchment paper to overhang the long sides of the pan. This will make it easy to lift the cooled bars out of the pan and cut them into squares.
Use a wooden spoon or spatula to stir in the ingredients. This will prevent overmixing the cookie dough.
Cool the bars completely before cutting into squares. Cooled bars cut cleaner than warm cookie bars.