Line the slow cooker with heavy-duty foil, leaving enough overhang to fold over the potatoes.
Add cubed red potatoes, most of the bacon, 1 1/2 cups cheese, ranch seasoning, salt, and pepper. Toss to combine.
Fold foil over the potatoes to make a packet inside the slow cooker.
Cover and cook on Low for about 4 hours, until potatoes are tender.
Open the foil carefully. Sprinkle remaining cheese over the potatoes.
Cover again briefly until cheese melts.
Top with remaining bacon and green onions before serving.
Notes
Use red potatoes because they hold their shape better than russets in the slow cooker. Measure the ranch seasoning; too much can make the dish too salty. Keep the foil packet sealed while cooking so the potatoes steam properly. Store leftovers refrigerated for up to 4 days and reheat gently.
Keyword cheesy ranch potatoes, potato side dish, slow cooker potatoes