Preheat oven to 350 degrees.
In a large skillet, cook the bacon. Place bacon on a paper towel lined pate to drain and set aside. Leave bacon drippings in the pan.
Season chicken breasts with salt and pepper.
Add butter to the pan and cook chicken breast until brown on both sides. Remove from the pan and place in a 9 x 13 inch baking dish.
Add the onion to the pan and cook for 1 minute