In a large skillet, cook bacon in batches over medium heat until crisp. Remove to paper towels to drain.
In a greased 4- or 5-qt. slow cooker, layer a third of each of the following: potatoes, reserved bacon and cheese. Repeat layers twice. In a large bowl, whisk eggs, milk, salt and pepper; pour over top. Cook, covered, on low until eggs are set, 4-5 hours. Turn off slow cooker. Remove crock insert to a wire rack; let stand, uncovered, 30 minutes before serving. If desired, sprinkle with parsley.
