Preheat the oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
In a large mixing bowl, whisk together the melted butter, light brown sugar, and granulated sugar until smooth and combined.
Add the eggs one at a time, whisking well after each addition, then stir in the vanilla extract.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
Fold in the rolled oats, chocolate chips, chopped walnuts, chopped pecans, and dried cranberries until evenly distributed.
Transfer the cookie dough to the prepared baking pan and press it down evenly with a spatula.
Bake for 22 to 25 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out with a few moist crumbs.
Remove from the oven and allow the bars to cool completely in the pan on a wire rack.
Once cooled, use the parchment paper overhang to lift the bars out of the pan and cut into 16 squares.