Spray large nonstick skillet with nonstick cooking spray. Heat over medium heat until hot. Add spinach, mushrooms, salt and nutmeg; cook 2 to 3 minutes or until thoroughly heated, stirring occasionally. Remove mixture from skillet; set aside.
Let skillet cool 1 minute. Wipe skillet clean with paper towel. Spray skillet again with cooking spray; return to medium heat. Pour half of egg product into skillet; cook 3 to 4 minutes or until set but still moist on top, lifting edges occasionally to allow uncooked egg product to flow to bottom of skillet.
Top 1 side of cooked egg product with half of the spinach mixture and half of the cheese. With pancake turner, loosen edge of omelet and fold other half over filling. Cover skillet; cook 1 minute. Remove omelet from skillet.
Repeat with remaining egg product, spinach mixture and cheese. Sprinkle each omelet with pepper. To serve, cut each omelet in half.