For this Instant Pot recipe, you'll want to consider is whether the vegetable has a similar cook time to the other ingredients. A few options are frozen corn, peas, and green beans. For softer, quick-cooking vegetables like summer squash, split the pressure cooking into two sessions. Release the pressure after 5 or 6 minutes, add the squash, and resume pressure cooking for 2 to 3 minutes. Leafy greens like spinach and kale should be added after cooking. The residual heat of the soup is enough to soften the greens.