Heat oil in a 12-inch pan with a lid over medium heat. Add in the onion, peppers, cumin, and coriander. Cook, stirring occasionally, until onions are translucent, 7-8 minutes.
Stir in the garlic and cook for 30 seconds.
Add in the quinoa, black beans, corn kernels, tomatoes, and salt and pepper. Give it a large stir.
Pour in the liquid, put the lid on, and bring it to a boil. Then turn the heat down to low and let it simmer for 20-23 minutes or until all the liquid is absorbed.
Let it sit for 5 minutes or so and fluff with a fork. Right before serving stir in the fresh cilantro.
Spoon the Mexican quinoa into bowls and garnish with fresh cilantro, avocado, and scallions. Serve with wedges of lime.