Preheat oven to 350º. Grease a 9x13-inch baking pan. In a medium bowl, stir together flour, oats, brown sugar, baking soda and salt. Add melted butter and stir to combine. Press 1/2 of batter into the bottom of baking pan. Bake for 10 minutes.

Remove from oven and sprinkle with chocolate chips and walnuts. Drizzle caramel sauce over top and crumble remaining oat mixture evenly on top, patting down lightly. Bake for an additional 15 to 20 minutes or until the top is golden; cool before cutting into bars.