Cut bread in half lengthwise; carefully hollow out top and bottom of loaf, leaving a 1-in. shell. Cube the bread removed into 1-inch cubes. In a large bowl, beat the eggs, milk, pepper and salt. Add bread cubes and toss to coat; set aside.
In a medium skillet, cook sausage and onion over medium heat until brown until meat is browned; drain. Add to the bread mixture. Spoon filling into bread shells; sprinkle with cheese. wrap each loaf in foil. Bake for 20-25 minutes or until cheese is melted. Cut into serving-size slices.