Peel the lemon with a vegetable peeler into wide strips. Place the peels in a medium saucepan (reserve the peeled lemon). Add the water, ginger, and salt and bring to a boil over high heat. Meanwhile, place the quinoa in a fine-mesh strainer and rinse under cool water for about 1 minute.
When the water comes to a boil, reduce the heat to medium-low and add the rinsed quinoa and steel-cut oats. Stir, then cover and simmer until the quinoa grains start to pop open and the oats are tender but chewy, 20 to 25 minutes. Meanwhile, halve the peeled lemon.
When the grains are ready, remove from the heat. Squeeze the juice from the lemon halves in to taste, 2 to 3 tablespoons. Remove the lemon peels and serve immediately.
