DEVILED Eggs: Remove cooked egg yolks from whites. Mix yolks, mayo and mustard in bowl. Pipe mixture back into egg white halves. Set aside.
FOR each salad: Arrange 1 cup spinach on serving plate. Top with 2 bacon slices, 2 Tbsp. mushrooms and 3 onion rings. Garnish with 2 Deviled Egg halves. Serve 2 Tbsp. dressing on the side or drizzled over the top.