Preheat your oven to 350°F (175°C) to ensure even baking.
Lightly grease your 9x13 inch baking dish with cooking spray or a thin layer of butter to prevent sticking.
In a large mixing bowl, combine the graham cracker crumbs, shredded coconut, melted butter, sweetened condensed milk, and vanilla extract. Mix well with a spatula.
Pour the mixture into the prepared baking dish and press down firmly into an even layer using a spatula.
Bake the base in the preheated oven for about 20 minutes, until the edges are golden brown.
While baking, break the milk chocolate bars into pieces and melt them in a microwave-safe bowl, heating in 30-second intervals and stirring until smooth. Stir in the vegetable oil.
After the base cools slightly, pour the melted chocolate over it and spread evenly with a spatula.
Refrigerate the bars for at least 2 hours to allow the chocolate to set.
Remove from refrigerator and cut into squares or rectangles to serve.