Add 2 cups of chicken stock to a medium saucepan. Place over medium-high heat and bring to a boil.
Add the quinoa, cover, and bring back up to a boil. Reduce the heat to a simmer and cook for another 12 minutes.
Remove the saucepan from the heat and fluff the quinoa with a fork. Recover the pot again and allow it to sit to the side for 15 minutes.
Preheat your oven to 350 degrees F.
While the quinoa sits, heat the olive oil in a large skillet over medium heat.
Add the onion and garlic and cook, stirring occasionally, for 3-5 minutes until the onion has softened. Add the mushrooms and allow them to cook until they are soft. Add in the spinach and artichokes and stir to combine. Cook until warmed through.
Turn off the heat but keep the skillet on the burner. Add the cream cheese, 3/4 cup of Parmesan cheese, and all the feta cheese to the spinach mixture.
Once all the cheese is melted and evenly distributed, stir in the quinoa.
Cut off the tops of the peppers and remove the seeds. Divide the quinoa mixture between the peppers, filling them with a heaping amount. Use the remaining Parmesan to top each pepper.
Place the peppers carefully into a high-sided baking dish. Pour 1 cup of chicken stock into the bottom of the baking dish. Cover the dish with aluminum foil.
Cook for 30 minutes. Then carefully remove the foil from the dish. Return to the oven and cook for another 15 minutes or until the Parmesan cheese is melted and slightly browned.
Use a spatula or tongs to take the peppers out of the baking dish. Serve warm with a salad or your favorite sides.
Notes
Make this dish vegetarian by swapping out vegetable broth for chicken stock.
To drain the thawed spinach, wrap it up in a double layer of paper towels and then use your hands to squeeze out as much moisture as possible, being careful not to pop the towels open.