In this pork loin recipe, I've included rutabaga for a lower carb potato substitute, along with green beans, red pepper, and red onion for a great mix of flavors and textures. Feel free to use potatoes instead of the rutabagas if you're not low carb.
Other options include carrots (or other root vegetables), fennel, cauliflower, brussels sprouts, or any other firm vegetable that can stand up to slow cooking. Avoid veggies that cook quickly and have a lot of water, like asparagus or zucchini.