The night before, or a few hours before, take the bread out of the package and let it sit out. It's best if it is not too fresh/soft. It isn't a tragedy if you forget.
Preheat the oven to 350 degrees.
Tear the bread into bite-sized pieces.
Finely chop the onion.
Melt the butter and put it into a large bowl.
Pour the bread cubes into the melted butter, using your hands to coat the bread with the butter.
Add the onion to the bread and combine with your hands.
Sprinkle the poultry seasoning and thyme leaves over the bread. Mix with your hands.
Grease a 9x13 inch baking dish. You can use spray with nonstick cooking spray if you prefer.
Pour the bread mixture into the prepared dish.
Sprinkle the milk over the bread, working it in slightly. I sprinkled 1/4 cup at a time so nothing became too soggy.
Bake for 35 to 40 minutes until browned.