Cut squash in half lengthwise. Scoop out seeds; discard. Put squash halves, cut sides down, in a microwave-safe bowl. Cover lightly with waxed paper. Microwave at HIGH 20 minutes or until tender. Let stand 10 minutes. Scrape inside of squash with a fork to remove spaghetti-like strands to measure about 4 cups (will probably need to hold the squash with your oven mitts).