Line an 8×8 inch square baking pan with parchment paper, leaving an overhang on the sides for easy removal.
In a medium bowl, whisk together the gluten free oat flour and salt until combined.
In a large bowl, using a hand mixer or stand mixer, beat the softened butter, light brown sugar, and granulated sugar on medium speed until creamy and smooth, about 2-3 minutes.
Add the vanilla extract and milk to the butter and sugar mixture and beat until combined.
Gradually add the flour mixture to the wet ingredients, mixing on low speed until just combined and a dough forms.
Fold in the mini semisweet chocolate chips evenly throughout the dough.
Press the cookie dough evenly into the prepared baking pan, smoothing the top with a spatula.
Refrigerate the dough bars for at least 1 hour or until firm enough to cut into bars.
Once firm, lift the cookie dough out of the pan using the parchment paper overhang and cut into 12 equal bars.
Store the gluten free cookie dough bars in an airtight container in the refrigerator for up to 5 days.