In a large bowl, whisk together the eggs and milk.
Stir in the crumbled bacon, diced ham, cooked sausage, chopped green onions, shredded cheddar cheese, salt, and pepper until well combined.
Lightly grease a 7-inch round baking dish that fits inside your Instant Pot.
Pour the egg mixture into the prepared dish.
Pour 1 ½ cups of water into the inner pot of your Instant Pot and place the trivet inside.
Carefully lower the baking dish onto the trivet. Secure the lid, ensuring the steam release valve is set to 'Sealing'.
Select the 'Pressure Cook' or 'Manual' function and set the timer for 30 minutes at high pressure.
When the cooking time is up, allow the pressure to release naturally for 10 minutes, then carefully switch the valve to 'Venting' to quick release any remaining pressure.
Using oven mitts, carefully lift the dish out of the Instant Pot.
Let it cool slightly before slicing and serving warm.
Cover the baking dish loosely with aluminum foil before cooking to prevent condensation from dripping onto the casserole.
