Preheat your oven to 350°F (175°C). This step is crucial as it ensures your bars bake evenly.
Grease a 9x13-inch baking pan with butter or line it with parchment paper for easy removal of the bars later.
In a large mixing bowl, combine the all-purpose flour, salt, and oats. Stir until evenly mixed.
In another bowl, cream the softened butter and brown sugar together until light and fluffy. This should take about 2-3 minutes.
Add the lightly beaten egg and vanilla extract to the butter-sugar mixture. Mix until well incorporated.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix.
Gently fold in the semi-sweet chocolate chips, butterscotch chips, and flaked coconut until evenly distributed.
Spread the mixture evenly in the prepared baking pan. Use a spatula to smooth the top.
Pour the sweetened condensed milk over the top of the batter, spreading it evenly with the spatula.
Place the pan in the preheated oven and bake for 25-30 minutes or until the edges are golden brown and the center is set.
Allow the bars to cool in the pan for at least 15 minutes before transferring them to a wire rack to cool completely. Once cool, cut into squares and enjoy!
