Wash squash, cut in half lengthwise, and discard seeds.
Place squash, cut side down, in a Dutch oven, add 2 inches water.
Bring water to a boil, cover and cook 20 minutes or until squash is tender.
Drain squash, and cool.
Using a fork, remove spaghetti-like strands.
Measure 3 cups of strands, set aside.
Reserve remaining strands for other uses.
Steam vegetables 5 to 7 minutes or until crisp-tender, drain well.
Combine squash strands and vegetables, tossing gently.
Cover to keep warm, set aside.
Saute garlic in margarine in a small saucepan, remove from heat.
Add milk, cheese, butter flavoring, and seasonings to saucepan.
Cook over low heat, stirring constantly, until mixture is hot (do not boil).
Spoon cheese mixture over vegetable mixture, tossing gently.