Preheat the oven to 375 degrees. Lightly oil a 9x13 baking dish. Rinse quinoa in a fine mesh sieve for 30 seconds.
On the stove in a small pot or in the microwave, heat the vegetable broth until simmering.
Combine all ingredients, except for the cheese and garnishes, in the 9x13 baking dish. Stir to combine.
Cover tightly with foil. Bake at 375F for 30 minutes on the middle oven rack. Remove the foil and stir. The quinoa should be cooked through but the casserole will still be liquidy.
Bake for 15 minutes, or until the quinoa is firm and the excess liquid evaporates.
Top with the shredded cheese and return to the oven for 5 minutes, until the cheese is melted and bubbly.
Remove from oven and let cool for 5 minutes before serving. Serve topped with avocado or guacamole, fresh cilantro and salsa.
