Place potatoes in large saucepan; cover with water 1 inch over top of potatoes. Bring to a boil. Reduce heat; simmer 10 to 15 minutes or until tender when pierced with a fork.
Heat oil in small skillet over medium heat. Cook and stir leek 2 to 3 minutes or until tender, but not brown. Remove from heat; set aside.
Drain potatoes, reserving cooking liquid. Add cheese, butter and cooked leek to potatoes. Mash with potato masher until fairly smooth, adding 1/2 to 3/4 cup of reserved cooking liquid for desired consistency.
While mashing, add salt and pepper to taste. Fold in turkey bacon.
