Heat oven to 400°F. Cut bread loaf horizontally in half. Cut bread halves crosswise in half to make 4 pieces (to fit on cookie sheet). Arrange on large ungreased cookie sheet; set aside.
In 10-inch skillet, cook beef and onion over medium-high heat 5 to 7 minutes, stirring occasionally, until beef is brown; drain. Stir in pizza sauce. Spread beef mixture over bread. Sprinkle with tomato, bacon and cheese.
Bake 12 to 15 minutes or until pizza is hot and cheese is melted.