Combine first 5 ingredients in a bowl; stir well, and set aside.
Coat a large nonstick skillet with cooking spray; place over medium-high heat until hot. Add zucchini, bell pepper, and green onions; cook, stirring constantly, 5 minutes or until tender. Stir in corn. Pour egg mixture over vegetables; cover, reduce heat to medium-low, and cook 15 minutes or until set.
Sprinkle cheese over frittata. Wrap handle of skillet with foil; broil 2 minutes or until cheese melts. Serve immediately.