Preheat the oven to 350°F (180°C) and lightly grease a 9x13-inch (about 23x33 cm) baking dish with olive oil or cooking spray.
Steam, or boil the butternut squash for 10 to 15 minutes or until tender. For baking, preheat the oven to 375°F (190°C) and roast the squash for about 30-35 minutes until it's fork-tender.
In the meantime, heat the oil in a large skillet over medium-high heat until hot, then add the onion and cook for about 2-3 minutes or until they're lightly browned.
Next, add the black beans, drained butternut squash, green chiles, and spices (cumin, oregano, salt, and pepper). Stir everything together to combine and cook for about 5 minutes, occasionally stirring. Set aside.
To assemble the vegan enchiladas, evenly spread ½ cup (120 milliliters) of red enchilada sauce in the baking dish.
Lay out a tortilla and spread 1 tablespoon of sauce evenly over the surface of the tortilla.
Add ⅛ of the squash and black bean filling in a line down the center of the tortilla, then sprinkle with some vegan cheese (about 2 tablespoons).
Roll up the tortilla and place it in the baking dish, seam side down. Assemble the remaining enchiladas in the same way.
Next, evenly spread the remaining red enchilada sauce over the top of the enchiladas, and then sprinkle the remaining vegan cheese.
Bake for 20 to 25 minutes, or until the vegan cheese has melted and the tortillas are slightly crispy on the outside.