Preheat the oven to 375 degrees.
Cut the squash in half lengthwise, then scrape out the seeds. Place the two halves, cut side up, in a foil-lined shallow baking dish. Cover tightly with more foil and bake for 40 to 50 minutes, or until easily pierced with a fork.
When the squash is cool enough to handle, scrape the flesh away from the shell with a fork, using long downward motions to remove the spaghetti like strands.
Heat 1 tablespoon of the oil in a soup pot. Add the onion and sauté over medium heat until translucent. Add the garlic and continue to sauté until the onion is golden and just beginning to brown.
Add the spaghetti squash, canned and dried tomatoes, water, mushrooms, seasoning, oregano, and thyme. Bring to a rapid simmer, then lower the heat. Cover and simmer gently for 20 to 25 minutes. Season with salt and pepper.
Meanwhile, heat the remaining tablespoon of oil in a skillet. Add the turnips and sauté over medium-high heat, stirring frequently, until golden. Add the snow peas and continue to sauté, stirring, until the snow peas are bright green and tender-crisp. Top each serving with some of the turnips and snow peas, and serve at once.