Remove the lid of the instant pot and press the sauté button.
Add the oil, the butter and the onion and let sauté, stirring frequently until the onion is translucent, about 5 minutes.
Add the garlic and continue to sauté, about a minute.
Press the cancel button to turn off sauté, add the chicken broth, dried oregano, black pepper and salt, then stir everything together. Stir in the drained, rinsed rice.
Replace the lid and turn it to locking position, making sure the steam release valve is set to “sealing.”
Press the “Pressure Cook” button and set to 3 minutes on high pressure, (might be called “manual” button on some IP’s.)
Once the rice is done, let the instant pot naturally release for 20 minutes. (In my instant pot it will signal it is done by a series of beeps. Following those beeps it shows natural release time starting with L0:00. When it gets to L0:20 it has naturally released for 20 minutes.)
Following the 20 minute natural release, move the steam release valve to vent to let the rest of the steam release from the instant pot, then remove the lid.
Sprinkle in the lemon juice, lemon zest and chopped parsley, and toss it all together, fluffing the rice as you go!
Taste and add additional salt and pepper if needed to taste.
Serve with fresh lemon slices and extra chopped parsley on the top if desired for presentation!