Cook the onions: Heat olive oil in a large, deep skillet over medium heat: Add the onion and sauté for 2–3 minutes until translucent.
Cook the base: Add the garlic and cook for 30 seconds, just until fragrant. Stir in the taco seasoning, oregano, salt, pepper, Let them toast for about 30 seconds to bring out the flavor.
Add the veggies: Add the lentils, black beans, tomatoes (with juices), corn, and veggie broth. Stir everything together. Cover with a lid, turn the heat to medium-high, and bring it to a full boil.
Add the liquid: Once it starts boiling, lower the heat to medium-low and simmer for 5 minutes. After 5 minutes, take off the lid and stir in the rice.
Cover and cook: Cover again, bring it back to a boil, then reduce the heat to low and simmer for 20 minutes: While that cooks, grate your cheese and slice the green onions. Once the 20 minutes is up, remove the skillet from the heat but keep the lid on. Let it rest for 5 minutes.
Fluff the rice: Take off the lid, fluff the rice, and gently stir to mix the veggies: Top with shredded cheese and green onions. Add any extra toppings you like, and dig in!