Place potatoes in a large pot with water to just cover; bring to a boil, then reduce heat and simmer until just tender, 15 minutes.
Meanwhile, cook bacon over medium heat in a large skillet with onion until just crisp. Drain and set aside.
When potatoes are just tender, stir bacon mixture, creamed corn, evaporated milk, milk, margarine, cheese, salt and pepper into the pot. Heat, stirring, 10 minutes, until cheese and margarine are melted and mixture is thoroughly heated.