Cut squash in half crosswise; remove seeds. Place squash halves, cut side up, in a greased 15- x 10-inch jellyroll pan; add butter evenly to squash halves.
Bake at 350° for 45 minutes to 1 hour or until tender.
Drain oysters, reserving half of liquid. Place oysters and reserved liquid in a large saucepan; cook over medium-high heat, stirring occasionally, until oysters begin to curl. Stir in soup; spoon evenly into squash halves. Sprinkle with bacon and parsley.
Bake at 350° for 5 minutes.