Wash and prep all veggies by slicing as needed. Sauté peppers and onion with the butter or garlic butter for a couple minutes until beginning to soften.
Add remaining ingredients and sauté until cooked and beginning to wilt, you want veggies to still be a bit crisp. This took about 10 minutes for me.
Note: you’ll need a pretty big pan to sauté this in, so be sure that you choose something that will be large enough!