Heat oven to 350*
Cut squash lengthwise in half; discard seeds. Cut each half crosswise into thin slices; remove peels.
Place squash in large saucepan. Add enough water to cover squash. Bring to a boil on high heat; simmer on medium-low heat for 8 to 10 minutes or until squash is tender.
Meanwhile, cook bacon in skillet until crisp, stirring occasionally.
Remove bacon from skillet with slotted spoon, reserving 1 Tbsp. of the drippings in the skillet. Drain bacon on paper towels.
Add onions to reserved drippings; cook and stir 5 minutes or until crisp-tender.
Stir in flour and pepper; cook and stir 1 min.
Gradually stir in broth; cook and stir 2-3 min. or until thickened.
Remove from heat. Stir in 1 cup cheese.
Drain squash, arrange in 8- or 9-inch square baking dish; cover with half the sauce. Repeat layers; top with bacon and remaining cheese.
Bake 25-30  minutes or until squash mixture is heated through and cheese is melted.