For a hearty vegetarian option, try these stuffed portobello mushrooms. Gather large portobello mushrooms, quinoa, bell peppers, onions, garlic, spinach, feta cheese, and breadcrumbs. Start by cooking the quinoa according to the package instructions. In a pan, sauté the bell peppers, onions, and garlic until they are soft. Add the spinach and cook until wilted. In a bowl, mix together the cooked quinoa, sautéed vegetables, crumbled feta cheese, and breadcrumbs. Stuff each portobello mushroom cap with the filling and place them on a baking sheet. Bake in a preheated oven at 375°F for about 20-25 minutes or until the mushrooms are tender and the filling is heated through. These vegetarian stuffed portobello mushrooms are a satisfying and flavorful option for any meatless meal.