Preheat the oven to 350 degrees F. Lightly coat an 8- by 8-inch baking pan with cooking spray.
In a large bowl, whisk together the whole wheat flour, cinnamon, salt and baking soda.
In a medium bowl, whisk the egg. Whisk in the yogurt, melted coconut oil, water, maple syrup and vanilla extract.
Pour the yogurt mixture into the dry ingredients and stir to combine.
Stir in the oats and dried cranberries until combined.
Transfer the batter to the prepared baking pan and spread evenly.
Bake until a toothpick inserted in the center comes out clean, about 20 minutes.
Allow the bars to cool completely. Cut the bars into 24 pieces and remove from the pan.
Place the chocolate in a medium microwave-proof bowl and melt in the microwave on 50% power, stirring every 30 seconds.
Drizzle the chocolate over the bars. Serve.