1. Preheat oven to 375F. Line a 9×13-inch baking dish with parchment paper, leaving overhang on short sides; lightly coat paper with cooking spray. In a food processor, pulse together butter, confectioners’ sugar, flour and salt until mixture resembles coarse meal. Add oats and pulse until just combined. Press dough evenly into bottom of dish and bake until lightly browned and firm, about 20 minutes.
2. Scatter chocolate chips, walnuts, and raisins on top of crust. Drizzle with condensed milk and top with coconut. Bake until coconut is golden, about 20 minutes. Let cool completely in dish on a wire rack before cutting into 18 squares.
Store in an airtight container, at room temperature up to 3 days.