Preheat the oven to 350F. Spray 9x13 pan with cooking spray. You can also line the pan with aluminum foil and spray with cooking spray for easy clean-up/removal.
In a large bowl, combine the oats, flour, brown sugar, baking soda, and salt and whisk to combine. Add the melted butter and stir until crumbly.
In a small bowl, add the caramels and heavy cream. Microwave on 50% power for 3-4 minutes, stirring every minute or so until melted and smooth.
Place ½ of the oat mixture in the bottom of the prepared pan. Press to make an even layer. Pour over the caramel mixture and carefully smooth over the oat mixture. Sprinkle the chocolate chips (save a few for the top if you like) and nuts if using over the caramel. Sprinkle the rest of the oat mixture over top then sprinkle with a few chocolate chips if desired.
Bake for 20-25 minutes until the crust has turned golden brown and the caramel is bubbly. Allow the bars to cool completely before slicing. (I usually put them in the fridge for 1-2 hours to speed up the setting.)
Cut into bars and enjoy!
Tip: Wait until the gluten-free oatmeal bars are fully cool before slicing. Then the caramel and chocolate will be set so you get clean slices. You can speed up the cooling process by placing the bars in the refrigerator for 1 hour.Dairy-Free?To make these gluten-free oatmeal bars dairy-free, use dairy-free chocolate chips and a dairy-free caramel like this caramel sauce. You can also use vegan butter like Earth Balance buttery sticks in place of the butter.Storage: These bars will keep tightly covered or in an airtight container at room temperature for up to 3 days.To Freeze: You can freeze the entire rectangle of bars, or cut them into 24 slices and freeze them individually. Wrap the slices in parchment paper then store them in a large ziploc freezer bag for best results. You can also bake the bars in a disposable foil pan – then cover the whole pan with foil to freeze. The bars will keep frozen for 2-3 months.