Beat the eggs and soup in a medium bowl with a fork or whisk
Season with salt and pepper
Heat the butter in a12-inch ovenproof nonstick skillet over medium heat
Add the mushrooms, yellow onion and zucchini and cook until tender
Stir in the egg mixture
Reduce the heat to low
Cook for5 minutes or until the egg mixture is almost set but still moist
Heat the broiler
Sprinkle the cheese over the egg mixture
Broil the frittata with the top 4 inchesfrom the heat for 2 minutes or until the top is golden brown
Sprinkle with the green onions before serving
