Cook quinoa as per package instructions and undercook by 4 minutes. Add to a large mixing bowl.
Preheat oven to 350 F degrees and get 8 x 11 baking dish ready. Set aside.
Preheat large skillet on medium heat and add coconut oil. Add garlic and cook for 30 seconds mixing often. Add corn, bell peppers, jalapeno pepper and cumin. Mix and sautee undisturbed for 3 minutes, mix and sautee for another 3 minutes. Transfer to a bowl with quinoa.
To a bowl with quinoa and sauteed vegetables, add black beans, 3/4 cup cilantro, 1/4 cup green onions, 1.5 cup cheese, coconut milk and salt. Mix enough to combine all ingredients.
Transfer the mixture to 8 x 11 baking dish, sprinkle with remaining 0.5 cup cheese and bake for 30-40 minutes uncovered. Remove from the oven, sprinkle with remaining cilantro and green onions, and serve warm. No need to let the casserole to cool down.
Replacing the light coconut milk with equal parts whole milk or heavy cream alters the final richness and introduces dairy fats that brown differently under direct heat. Understanding how starches absorb liquids during baking prevents dense, heavy textures in grain-based dishes. Quinoa requires careful moisture management because it releases trapped water as it bakes in a casserole format. Undercooking the dry grain by four minutes on the stovetop leaves adequate room for it to absorb the coconut milk and vegetable moisture inside the 8 by 11-inch baking dish without turning mushy. Aromatics like garlic and cumin bloom efficiently in hot coconut oil, but maintaining medium heat stops the garlic from burning and turning bitter during the initial thirty-second saute. Bell peppers and corn benefit from remaining undisturbed for three-minute intervals in the skillet to develop mild charring on their surfaces. Thorough combination of the black beans, shredded Tex-Mex cheese, and chopped herbs distributes flavor evenly before the uncovered baking phase at 350 degrees Fahrenheit. Leftovers hold up well in a sealed container stored in the refrigerator for up to four days, and individual portions reheat reliably in a microwave or a 350-degree oven until steaming throughout. Freezing is technically possible, though the high moisture content from the vegetables and coconut milk can cause the thawed quinoa and melted cheese to separate into a watery texture upon reheating.