Preheat oven to 375F. Place squash, cut side down, on a baking sheet & cook until tender, about 45 minutes. Set aside to cool. Scoop out the inside & discard the seeds & strings.
Saute pine nuts & green onions in oil for 1 minute. Add mushrooms, zucchini, yellow squash & tomatoes & saute until just about tender, 5 minutes or so.
Stir in the remaining ingredients. Spoon the vegetable mixture into the squash shells. Serve immediately.