Preheat the oven to 350 degrees F, and lightly grease an 8-inch square or other 1 1/2 quart casserole.
In a pot with a tight-fitting lid (see notes), bring 1 1/4 cups of water to a boil. Stir in the rinsed and drained quinoa and the 1/2 teaspoon salt. Cover, reduce the heat to low, and simmer for 12-15 minutes or until the water is absorbed. Remove from the heat and rest, covered, for 5 minutes. Fluff with a fork and set aside, uncovered at this point.
While the quinoa is cooking, heat a large, lightly-oiled skillet over medium-high heat. Add the onion and sauté for 3 minutes or until softened and beginning to turn golden. Add the sausage and brown, crumbling it as it cooks. Stir in the bell pepper and the spices (cumin, coriander, black pepper, and 1/4 teaspoon salt), and sauté until the bell pepper is crisp-tender, about 3-4 minutes more.
Add the corn (it will quickly thaw if still frozen) and the drained black beans. Cook, stirring to incorporate, until warm throughout, about 1-2 minutes more.
Transfer the vegetable mixture to the pot with the quinoa (or a bowl large enough to hold everything), and add 3/4 cup (3 ounces) of the cheese and the parsley. Stir to thoroughly combine, and transfer to the prepared baking dish. (Optionally, if your skillet is oven-proof, you may bake the quinoa in that.)
Sprinkle with the remaining cheese and bake until the cheese is melted and the quinoa is hot throughout, about 10 minutes. Rest for 5 minutes before serving, sprinkle with additional cilantro or parsley, if desired, and enjoy.