Crack the eggs into a large mixing bowl. Season with salt and pepper. Beat the eggs and seasoning together well to combine.
Roughly dice the bell pepper. Add the diced bell pepper, grated cheese and dried oregano to the bowl with the beaten egg. Mix everything together well, distributing the flavorings evenly throughout the beaten egg mixture.
Lightly grease a 7 inch springform pan or Pyrex dish suitable for an instant pot. We have used a 7 inch pan as it is easy to add and remove from the instant pot safely. Pour the frittata mixture into the prepared springform pan/Pyrex dish. Note that if your frittata pan is too large it will be very difficult to add and remove safely from the instant pot.
Add a cup of water to the base of the instant pot. Lower the instant pot trivet into the pot. Carefully sit the filled frittata pan on the trivet inside the instant pot.
Place the lid on the instant pot, ensuring that it is set to ‘sealing’. Set to cook on high pressure for 12 minutes. After this time, let the steam release naturally for 5 minutes, then do a quick release to allow the rest of the steam to escape. Once it is safe to do so, open the instant pot. Carefully and safely remove the frittata from the instant pot wearing oven gloves. Slice into quarters to serve.