Melt margarine in medium nonstick skillet over medium-high heat. Add onions and bell peppers; cook 2 to 3 minutes or until vegetables are crisp-tender, stirring occasionally.
Meanwhile, in medium bowl, combine eggs, milk, salt and pepper; beat well.
Pour egg mixture over vegetables in skillet. Reduce heat to medium; cook 4 to 6 minutes or until eggs are set but still moist, stirring frequently.
To serve, spoon egg mixture onto warm tortillas; sprinkle with cheese. Roll up.