In a large, heavy-bottomed pot over medium heat add 2 tablespoons of the olive oil. Add the mushrooms and saute until the mushrooms have release their liquid, 2 to 3 minutes. Remove the mushrooms with a slotted spoon and place in a bowl. Set aside.
Add the remaining 2 tablespoons olive oil to the pot. Add the onion and cook until translucent, about 4 minutes. Add the rice and stir to coat, cooking for about 1 minute to toast.
Add half the red wine and reduce by half. Add 1 cup chicken stock and simmer until the liquid is completely absorbed. Repeat with the remaining chicken stock, 1 cup at a time, adding another cup only when liquid is completely absorbed. Add the remaining red wine and simmer for another 15 minutes or until liquid is absorbed.
Remove from the heat. Fold in the butter, sauteed mushrooms, Parmesan, and marjoram and season with salt and pepper.