Preheat the oven to 350
Using a paring knife, cut the top off of each of the peppers. Spoon out the inside core of the peppers and remove all seeds. Set aside.
Brown the sausage, mushrooms, and onions on the stove. Reduce to low heat.
Mix the quinoa with the sausage, mushrooms, and onions. Stir and slowly add the Worcestershire sauce. Mix in the mozzarella cheese & remove from heat.
Spoon the mixture into each pepper and stuff it to the top.
Place the stuffed peppers right-side-up into a baking dish or muffin pan. Bake for 20-30 minutes until stuffing is golden brown and crisp on top.
Depending on the size of your peppers and how much you pack in the stuffing, you might have enough to make a few extra.