Rinse the quinoa under cold water, then combine with 3 cups water in a medium saucepan and bring to a boil over high heat.
Reduce heat to low, cover, and simmer until the water is absorbed and the quinoa is tender, about 12 to 15 minutes; fluff with a fork.
Preheat the oven to 375°F (190°C) and spray a 9x9-inch or 9x13-inch baking pan with cooking spray.
Transfer the cooked quinoa to a large bowl. Stir in the marinara sauce, about two-thirds of the shredded cheese, 1 tablespoon of the basil, the olive oil, and salt and pepper to taste.
Spread the quinoa mixture evenly into the prepared baking pan, smoothing the top and pressing gently to compact.
Sprinkle the reserved cheese and remaining 1 tablespoon basil evenly over the top.
Bake for 40 to 45 minutes, or until the top is golden and the edges are set. Let rest briefly, then serve warm.
