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, combine the melted butter, light brown sugar, and granulated sugar. Stir until smooth and well combined.
Add the eggs and vanilla extract to the sugar mixture and beat until fully incorporated.
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 throughout the batter.
Spread the batter evenly into the prepared baking pan, pressing it down gently to create an even layer.
Bake in the preheated oven for 22 to 25 minutes, or until the edges are golden brown and a toothpick inserted in the center comes out with a few moist crumbs.
Remove from the oven and allow the cookie bars to cool completely in the pan on a wire rack.
Once cooled, use the parchment paper overhang to lift the bars from the pan and place on a cutting board. Cut into 16 bars and serve.