Spaghetti Squash Casserole

3 tablespoons butter or margarine 1 cup mushrooms fresh, sliced 1/3 cup leeks chopped 1/4 cup celery chopped 3 tablespoons sweet red bell pepper chopped 3[...]

1 each spaghetti squash halved and seeded * 1 pound beef ground 1 small green bell pepper diced 1 small sweet red bell pepper diced 1/2 small red onion diced[...]