Place oven racks in upper-third and lower-third positions in oven.

Preheat the oven to 400°F.

Coat two baking sheets with nonstick cooking spray or olive oil.

Cut each squash in half lengthwise and remove the seeds with a spoon. Cut a thin slice from the skin side of each squash half so it sits flat.

Brush each squash half with olive oil on the cut side, and season with salt and pepper. Place five squash halves on each baking sheet with the cavity side down.

Roast the squash on upper-third and lower-third racks of oven, switching pan positions halfway through cook time, until just tender when pierced with a knife, 30-35 minutes. Remove from oven and set aside. Leave the oven on.

Meanwhile, rinse the quinoa under cold water. In a medium saucepan combine quinoa with the salt and water. Bring to a boil over high heat, then reduce heat to medium-low. Cover and simmer until liquid is absorbed and quinoa is tender, about 15 minutes. Set aside.

While the squash and quinoa cook, cut the onion and carrots into a 1/4-inch dice. Remove stems from the mushrooms and thinly slice the caps. Mince the garlic.

Heat the oil in a large nonstick frying pan over medium-high heat. Add the onion, carrots, mushrooms, garlic, thyme, and salt. Cook, stirring occasionally, until vegetables are tender and mushrooms are lightly browned, about 12 minutes.

Stir in the cranberries and pecans and cook for 1 minute. Add the spinach and cook until just wilted, about 2 minutes. Remove from heat and stir in the quinoa (transfer everything to a large bowl if it won't all fit).

Turn the squash halves over so the cavities face up. Spoon quinoa mixture into each cavity, mounding the filling as necessary.

Bake on upper-third and lower-third racks of oven until filling and squash are heated through, about 10 minutes.

Check to see that squash are done. Remove from oven or add time as needed.

Transfer squash to a platter. If you like, season to taste with more salt and drizzle with a little olive oil before serving.