Chop the onion and the red bell pepper into small pieces. Heat the olive oil in a skillet and sauté onion and pepper until tender. Add garlic and sauté for a minute until fragrant.
Add zucchini chopped into small cubes and sauté until soft.
Add corn kernels, fresh spinach and sauté for 2 minutes cook the spinach through.
Remove from heat, add cooked quinoa, smoked paprika, dried oregano and salt. Stir to combine. Set aside.
Remove portobello’s stalks, and place them down-side into a baking tray. Bake them for 3-5 minutes, to slightly often at 375F. Be careful, when they begin to release juice, take them out of the oven, the time will vary due to the size of each portobello. At this point, you are looking to soften the mushrooms. Once tender, remove them from the oven.
After turning them up, divide the filling into the eight portobellos. Place them back in the oven for another 5 minutes or until fork-tender.
Use the portobello’s stalks as part of the filling if desired, you should add it together with the zucchini.If using medium to small portobellos, you won’t need to cook them down-side first or they will significantly reduce, that step is necessary with large mushrooms.Storage: Store in an airtight container for up to 2 days and reheat in the oven.