Place Reynolds™ Slow Cooker Liners inside a 5- to 6 1/2 -qt slow cooker bowl. Make sure that liner fits snugly against the bottom and sides of bowl and pull the top of the liner over rim of bowl.
In lined slow cooker, mix onions and margarine.
Cover and cook on high heat setting 30 to 35 minutes or until onions begin to slightly brown around edges.
Mix flour, Worcestershire sauce, sugar and pepper. Stir flour mixture and broth into onions. Cover and cook on low heat setting 7 to 9 hours (or high heat setting 3 to 4 hours) or until onions are very tender.
Prepare Cheesy Broiled French Bread. Place 1 slice bread on top of each bowl of soup. Serve immediately.
Method for Cheesy Broiled French Bread: Set oven control to broil. Place bread slices on rack in broiler pan. Sprinkle with cheese. Broil with tops 5 to 6 inches from heat about 3 minutes or until cheese is melted.