Rinse corned beef under cold tap water. Rinse well and pat dry with paper towel.
Add rinsed corned beef, quartered onion, crushed garlic cloves, pickling spices seasoning, and 4 cups of cold water into the Instant Pot.
Close lid and pressure cook on Manual at High Pressure for 70 minutes followed by Natural Release for about 15 minutes. If the floating valve doesn’t drop after 15 minutes, release the remaining pressure by turning the venting knob from sealing position to venting position. Open lid carefully.
While the pressure cooker is natural releasing, prepare the vegetables as described.
Set aside cooked corned beef and 3 cups of the hot liquid in a large serving bowl. There should be about 1 1/2 to 2 cups of liquid left in the pressure cooker. Add quartered red potatoes, carrots, and cabbage wedges in the pressure cooker.
Close lid and pressure cook on Manual at High Pressure for 2 – 3 minutes, followed by a Quick Release. Open the lid carefully.
On a chopping board, cut Corned Beef against the grain into 1/8 inch slices. Serve with cabbage wedges, red potatoes and carrots. Enjoy!