Heat the oven to 350 degrees. Cook the bacon, then chop it into bite-size pieces and set it aside.
Melt the butter in a large pot over medium heat. Sauté the onion, celery, and peppers until soft. Stir in the flour, then the sour cream, until well combined. Add the corn and most of the bacon bits and season with salt and pepper.
Pour the mixture into a 9- by 13-inch baking dish and sprinkle on the remaining bacon bits and the parsley. Bake for 30 to 45 minutes, until lightly browned. (Note: for a lower-fat version of this casserole, use half the bacon, butter, and flour).