Preheat the oven to 375 degrees F.
Drizzle the potatoes with the olive oil and toss them to coat. Roast until the potatoes are tender and the skin is slightly crisp, 20 to 25 minutes.
Use a spoon or small scoop to remove the insides, leaving a small margin of potato intact.
To the scooped out potatoes, add the Monterey Jack, cream cheese, sour cream, chives, garlic, and salt and pepper to taste. Mash until the mixture is totally smooth. Give it a taste and add more salt if necessary.
Scoop the mixture into the potato shells. At this point you can cover and refrigerate them until dinnertime. When you're ready, bake the potatoes in the oven until golden brown on top.