Crumble ground beef into a microwave-safe plastic colander; mix in onion and garlic. Place colander in large bowl. Microwave, uncovered, on HIGH 4 to 5 minutes, until pink color is gone from meat; Discard fat collected in bowl. Transfer meat to casserole or fondue dish. Mix in remaining ingredients except bread. Microwave, uncovered, on HIGH for 5 to 7 minutes, until cheeses melt and fondue bubbles. Stir to blend mixture.
Serve with bread cubes to twirl in mixture. Return to microwave oven to reheat, if necessary, or place over burner to keep warm while serving.
Makes 4 to 5 servings.