Preheat the oven to 350°F. In a large skillet, cook the bacon and onion over medium heat until the bacon is crisp, then drain.
In a large bowl, combine the remaining ingredients. Stir in the bacon mixture. Transfer to a greased 13x9-inch baking dish.
Bake, uncovered, until a knife inserted in the center comes out clean, 35 to 40 minutes. Let the casserole stand for 10 minutes before cutting. Letting the casserole rest for a few minutes allows it to firm up.
