Preheat oven to 375˚. Mist a 9- x 13-inch casserole pan with non-stick oil spray.
Add dry quinoa along the bottom of the pan, followed by water, canned tomatoes with liquid, beans, corn, optional veggies, and taco seasoning. Mix everything.
Cover pan with parchment paper, foil or a glass cover if you have one, and bake for 30 minutes.
Uncover, mix everything, and let quinoa soak up extra liquid for a few minutes. Sprinkle cheese over the top and place back in oven for 5 to 10 mins until cheese is melted.
Top with optional garnishes, including diced avocado, sliced jalapeño, chopped cilantro or fresh lime juice.
