PREHEAT oven to 375°F. Heat oil in large skillet on medium heat. Add leeks; cook and stir 8 to 10 min. or until tender. Stir in ham. Remove from heat; set aside.
PREPARE pie crust as directed on package for unfilled 1-crust pie using 9-inch pie plate. Sprinkle half of the cheese evenly onto bottom of crust. Top with leek mixture and remaining cheese. Beat eggs and half-and-half with wire whisk until well blended; pour over ingredients in crust.
BAKE 35 to 40 min. or until knife inserted in center comes out clean. Let stand 10 min. before serving.