Wash potatoes (peel them if you like, but I prefer to keep the skins on) and cut into large pieces. Place pieces into a large bowl.
Pour olive oil on the potatoes and mix until all potatoes are coated in oil. Add ranch packet, garlic powder, dried minced onion, and Parmesan cheese and mix until almost all the potatoes are coated in seasonings.
Dump potatoes into the slow cooker and season with salt and pepper, if desired.
Cook on low for 5-6 hours (I have kept them in for up to 7 hours and they still turned out fine, they will just get softer the longer they cook. If you wanted to cook them longer, you could always turn them into mashed potatoes).
Top with shredded Parmesan cheese (or any other cheese) and serve.
We like to serve these potatoes with Grilled Chicken and Salad.