Preheat the oven to 400 degrees F. Spray a baking sheet with nonstick cooking spray and place the mushrooms, stem side up, and set the sheet aside.
Heat 1 tablespoon olive oil in a saute pan over medium heat and saute the shallots, garlic and capers until fragrant, about 2 - 3 minutes.
Add the cooked quinoa, sauteed vegetables and cheese to a mixing bowl. Stir to combine. Toss with the fresh basil and crushed red peppers. Season with salt and pepper.
Spoon the mixture into each of the mushrooms, about 1 teaspoon into each (depending on the size). Bake in the center of a warmed oven until the mushrooms have softened and the topping begins to brown, about 20 - 25 minutes. Serve immediately.
This recipe is easily doubled (or even tripled) if you're feeding a crowd or taking them to a party.