Preheat your oven to 350°F (175°C). Grease or line a 9x13 inch baking pan with parchment paper, allowing some overhang for easy removal later.
In a medium bowl, whisk together the 3 cups of all-purpose flour, 1 teaspoon of baking soda, and 1 teaspoon of salt. Set this mixture aside.
In a large mixing bowl, cream together the 2 cups of unsalted butter and 2 cups of packed light brown sugar until the mixture is light and fluffy. This should take about 3-5 minutes with an electric mixer on medium speed.
Gradually add the dry flour mixture to the creamed butter and sugar, mixing until just combined. Then, stir in the 3 cups of quick-cooking rolled oats until evenly distributed.
Press half of the oat mixture into the prepared baking pan to form a base. Make sure to spread it evenly.
In a small bowl, mix the 3 tablespoons of all-purpose flour with the 1 cup of semi-sweet chocolate chips and ½ cup of chopped pecans. Spread the 1 cup of dulce de leche over the pressed oat layer, then sprinkle the chocolate chip and pecan mixture evenly on top.
Crumble the remaining oat mixture over the chocolate and caramel layer. It doesn’t need to cover completely; some gaps will allow the chocolate and caramel to peek through.
Place the pan in the preheated oven and bake for 25-30 minutes or until the top is golden brown and the edges are bubbling.
Once baked, remove the pan from the oven and let it cool completely in the pan. Use the overhanging parchment paper to lift the bars out of the pan. Cut into squares or rectangles as desired.
