Preheat the oven to 400°F. Line a baking sheet with parchment paper. Halve the squash with a sharp knife. Using a spoon, scoop out the seeds.
Brush the squash halves insides with olive oil. Season with salt and pepper. Then place them cut side down on the baking sheet and bake in the preheated oven for 30-40 minutes. It's baked when you can pierce the flesh part of squash with a fork.
While the squash halves are baking, place rinsed quinoa in a small sauce pan over medium high heat. Toast them for 1-2 minutes. Add in broth or water, bring it to a boil on high, then cover and reduce the heat to low. Cook for 15 minutes or until the liquid is absorbed. Remove the pot from the heat and let stand for 5 more minutes, covered. After 5 minutes, uncover and fluff the quinoa with a fork.
Heat a skillet over medium heat. Add in 1 tablespoon of olive oil. Once hot, add in chopped onions, cook for about 5 minutes or until golden, stirring occasionally. Add in minced garlic and stir for 30-60 seconds, until fragrant. Transfer the onions and garlic mixture to a plate. Set aside.
In the same skillet, add in 1 tablespoon of olive oil and place on medium high. Once hot, add in sliced mushrooms. Cook for about 5-7 minutes until they are golden, stir occasionally.
Add in onion and garlic, along with spinach. Cook for 2-3 minutes until spinach is wilted. Add in chickpeas and cook for 5 more minutes.
Add in cooked quinoa along with salt, pepper, cumin, garlic powder and onion powder. Add half of the lemon zest and juice of half the lemon. Stir until combined. Turn off the heat.
Once the squashes are baked through, take them out of the oven. Fill them with as much filling as possible (save the rest for the side). Top each squash with the rest of lemon zest, feta cheese and walnuts. Serve with lemon quarters. Enjoy!