Combine quinoa and vegetable broth in a medium saucepan. Bring to a boil over high heat, cover, reduce heat to medium-low and simmer for 20 minutes, or until the liquid is absorbed and quinoa is fluffy. Fluff the quinoa with a fork after cooking.
Remove portobello’s stalks, and place them gill side down onto a baking sheet. Bake the mushrooms for 3-5 minutes, to slightly soften. Once the mushrooms begin to release their juices they are ready to be removed from the oven.
While the quinoa is simmering and the portobello mushrooms are baking, heat the olive oil in a large nonstick skillet. Once the oil is heated, add in the onion and pepper and saute until tender about 3-5 minutes. Add in the garlic and saute for a minute until just fragrant. Add the zucchini and ½ teaspoon salt and saute until just tender, 3-5 minutes. Add in the corn and spinach and continue to saute until the spinach has wilted and the corn is warmed through.
Remove the vegetable mixture from the heat. Stir in the cooked quinoa, with the paprika, oregano, and remaining ½ teaspoon of salt. Stir to combine. Set aside.
Remove the mushrooms from the oven and turn them over to reveal their cavity. Generously stuff with the vegetable quinoa filling. Return to the oven and bake for an additional 5-8 minutes, or until fork-tender.
Notes
Portobello Mushrooms: The filling makes enough for 8 portobellos. However, the filling is great served alone if you want to stuff fewer mushrooms. Use large portobellos for this recipe. To clean, simply wipe them down with a damp paper towel to remove any dirt. Do not season the mushroom itself with salt, as this will draw out too much liquid and make the mushrooms tough.Portobello Stalk: Feel free to dice up the portobello’s stalks and add to the filling along with the zucchini. Storage: Store any leftover stuffed mushrooms in an airtight container in the refrigerator for up to 3 days. Reheat in a 375-degree F oven to warm through. Store any leftover vegetable quinoa in a separate airtight container for 3-5 days.