Directly on sheet pan, toss onions and peppers with salt and pepper, italian seasoning, and a little bit of olive oil. Add sausage to mixture, and spread evenly on pan.
Cook at 400F for about 25 minutes. (I used sausages that were already cooked. If you’re cooking with uncooked meat, make sure you cook chicken sausages to an internal temp of 165F, pork to 160F.)