Preheat the oven to 350°F (175°C) and grease an 8x8 inch baking dish.
In a large mixing bowl, whisk together the eggs, milk, maple syrup, vanilla extract, cinnamon, and salt until homogenous.
Stir the cooked quinoa and blueberries into the liquid mixture until evenly distributed.
Pour the mixture into the prepared baking dish and distribute the quinoa evenly with a spatula.
Scatter the chopped walnuts over the top surface.
Bake for 45 minutes or until the center is set and the edges are golden brown.
Remove from the oven and allow to cool for 10 minutes to firm up before slicing into portions.