Turn on the Instant Pot and select the Sauté function. Add olive oil and let it heat.
Add the diced onion and sauté for about 2 minutes until soft and slightly translucent.
Add the minced garlic and sauté for 30–45 seconds until fragrant, being careful not to burn it.
Stir in the orzo pasta and cook for about 30 seconds, allowing it to lightly toast.
Turn off the Sauté function. Pour in the vegetable broth and gently stir to combine.
Add the zucchini, summer squash, carrots, and green beans. Do not stir after adding the vegetables.
Pour the crushed tomatoes evenly over the top without stirring.
Close and lock the Instant Pot lid. Set to High Pressure and cook for 2 minutes.
Allow the pressure to build naturally, then carefully release the pressure using the quick-release method.
Open the lid and stir in the baby spinach until wilted.
Add garlic granules, Greek seasoning, and lemon juice if using. Season with salt and freshly ground black pepper to taste.
Stir well and serve warm.