PREHEAT oven to 350°F (180°C). Line baking sheet with parchment paper.
HEAT large nonstick skillet over medium-high heat. Add oil, then mushrooms, onion and garlic and cook 6 to 7 minutes or until mushrooms are soft. Stir in spinach and cook until wilted, about 1 minute. Remove from heat and let cool to room temperature, about 10 minutes.
COMBINE mashed potatoes, quinoa, cheese, Hellmann's® Real Mayonnaise, egg, lemon peel, salt and if desired, ground black pepper to taste in large bowl. Stir in mushroom mixture until blended.
SCOOP mixture with 1/4 cup (60 mL) measuring cup onto prepared baking sheet. Pat tops down using bottom of cup to form patties.
BAKE in centre of oven 30 minutes or until golden brown.