Put the Monterey Jack, Cheddar, parsley, bacon and onion whites in a bowl and mix well.
Cut the bread in strips in one direction, being careful not to cut all the way through the loaf. Rotate the bread 90 degrees and cut in the other direction to create small squares across the top of the loaf. Move slowly and use caution. Place the bread on a large sheet of aluminum foil.
Stuff the cheese mixture in between the rows of squares. Mix the melted butter and ranch dressing, then drizzle over the top. Wrap the loaf in the foil and bake for 25 minutes. Open the foil and continue to bake until heated through and the cheese is melted and bubbly, another 10 minutes. Sprinkle with the onion greens and serve immediately.