Gather all ingredients. Preheat the oven to 375 degrees F. In a large bowl, combine eggs, milk, Toby’s Feta Cheese Dressing & Dip, and dijon mustard. Mix well, breaking up the yolks. Add in the mushrooms, onion, garlic, spinach, thyme, and cheese. Mix well until evenly combined.
Line a pie dish with the ready made pie crust and poke holes along the bottom and sides, then fill with the filling. Bake for 30 minutes until the center is firm and the crust is golden brown.
Let cool and slice. Plate and drizzle over with more Feta Cheese Dressing. Serve and enjoy your Mushroom & Spinach Quiche!