Preheat oven to 350°F. Beat eggs lightly in medium bowl. Add spinach, onions and Canadian bacon; mix well.
Spoon evenly into 12 medium muffin cups sprayed generously with cooking spray, filling each cup about two-thirds full. Use fork to break up larger crumbles of cheese; sprinkle evenly over batter in cups.
Bake 25 to 30 min. or until golden brown. Serve warm.