Turn Instant Pot to sauté. When hot, add olive oil, onion and bell pepper. Sauté until slightly tender, approximately 3-4 minutes.
Add the garlic and jalapeño and stir.
Turn the sauté function off. Add the water, oregano, cumin, chili powder, and salt. Stir.
Add in rice in a layer. Do not stir.
Add the corn and black beans. Do not stir.
Pour in the enchilada sauce. Do not stir.
Close the lid and seal the steam release valve. Press the Pressure Cook (or Manual) button, high pressure, and set time for 5 minutes. Once the cooking time is complete, let sit undisturbed for 3 minutes (natural release). Then carefully quick release the remaining steam.
When the pin in the lid drops down, open the lid stir everything together and taste for salt and tenderness of the rice* (if rice isn't tender enough, cover and let sit a few minutes).
Add the cheese, cover with a lid, and let it melt before serving.
Serve topped with fresh cilantro and avocado, sour cream, and hot sauce, if desired.