Begin by thoroughly washing and chopping the zucchini, cauliflower, and bell peppers into bite-sized pieces. Dice one onion and mince three cloves of garlic. Gather all your ingredients to ensure a smooth cooking process.

Set your Instant Pot to the 'Sauté' function and let it warm up for a couple of minutes. Add the diced onion and minced garlic, sautéing until fragrant and translucent, about 2-3 minutes.

Next, stir in the diced bell peppers, zucchini, and cauliflower, cooking for an additional 3-5 minutes until they begin to soften.

Once the vegetables are tender, lower the heat and stir in the cream cheese. Allow it to melt slightly before adding in the vegetable broth and Italian seasoning.

Mix everything well until fully combined, ensuring that each ingredient is coated in the creamy mixture.

Secure the Instant Pot lid, set the valve to the 'sealing' position, and select the 'Pressure Cook' setting on high for 10 minutes.

Once the cooking time is complete, carefully perform a quick release of the pressure by switching the valve to 'venting.' Stir the mixture gently after removing the lid.

Stir in the shredded cheddar cheese carefully, letting the residual heat melt the cheese as you mix.

Spoon the delightful casserole into bowls, serving it hot for maximum flavor.