Preheat an oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
Mix the graham cracker crumbs, butter, and sugar in a bowl. Press the mixture into the prepared baking dish to form a crust. Combine the coconut, sweetened condensed milk, and pecans in another bowl until well mixed. Spread coconut mixture over the cracker crust.
Bake in the preheated oven until set, about 15 minutes. Set aside to cool completely, about 1 hour.
Melt the chocolate bar and peanut butter in a small saucepan over very low heat, cooking and stirring until smooth, about 2 minutes. Spread the chocolate mixture evenly over the cooled coconut bars. Cool until set, about 15 minutes. Cut into bars before serving.