Prep oven and pan. Preheat oven to 350°F (177°C). Line an 8×8-inch pan with aluminum foil or parchment paper and spray with cooking spray. Lining your pan is highly recommended for ease of cleanup due to the stickiness of the caramel; set pan aside.
Combine wet ingredients. In a large mixing bowl, whisk together the melted butter, brown sugar, and vanilla until smooth.
Add dry ingredients. Add the flour, oats, baking soda, and salt, and stir with a wooden spoon or spatula until combined. Mixture will be thick.
Bake half of the dough. Add half of the mixture to the prepared pan and smooth the top. Set the remaining dough aside. Bake in a preheated 350°F for 10 minutes.
If making caramel: Combine caramels and cream in a medium saucepan, and heat over medium-low heat to melt, stirring nearly continuously, until mixture can be stirred smooth. Optionally stir in 1/2 teaspoon salt, or to taste. Set aside. You can also use store-bought caramel sauce (depending on brand, caramel might not be as thick and pronounced in flavor).
Finish prep for bars. After 10 minutes, remove pan from the oven and sprinkle with the chocolate chips. Slowly pour the caramel sauce over the chocolate, leaving a small border to the edge. The caramel has a tendency to stick to the foil, so I make sure to not spread the caramel right to the edge. Crumble the remaining oatmeal cookie dough over the top.
Finish baking. Return pan to oven and bake for about 15-18 minutes, until edges are lightly browned and center is bubbling slightly. If using a glass pan, your bars may take slightly longer.
Allow to cool. Allow bars to cool for 1-2 hours completely in the pan before slicing and serving to allow the caramel time to firm up. (Time may vary on cooling, and may take longer). You can speed up the process and cover the bars and place in the fridge.