Select saute setting on a 6-qt. electric pressure cooker. Adjust for medium heat; add oil. When oil is hot, cook and stir sausage and onion until sausage is no longer pink and onion is tender, 5-7 minutes, breaking up sausage into crumbles; drain. Press cancel., Stir in mushrooms and broth. Add quinoa (do not stir). Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 2 minutes. Quick-release pressure. , Stir in pizza sauce, pepperoni and green pepper; cover and let stand until pepper softens slightly, 5-10 minutes. Sprinkle servings with cheeses. If desired, serve with optional toppings., , Slow-cooker option: In a large skillet, heat oil over medium heat; cook sausage and onion until sausage is no longer pink, 5-7 minutes, breaking up sausage into large crumbles. Drain. , Transfer sausage and onion to a 4- or 5-qt. slow cooker. Stir in mushrooms, broth and quinoa. Cook, covered, 5 hours; stir in pizza sauce, pepperoni and green pepper. Cook, covered, 1 hour or until pepper is tender. Sprinkle servings with cheeses. If desired, serve with optional toppings.