Place egg substitute (or eggs) and milk in mixer bowl. Attach bowl and wire whip to the KitchenAid® Stand Mixer. Turn to Speed 2 and mix about 30 seconds. Set aside.
Heat oil in large skillet over medium heat until oil sizzles. Add bell pepper and onions. Cook about 1 minute, or until slightly tender. Stir in beans. Cook about 1 minute, or until thoroughly heated.
Reduce heat to medium-low. Pour egg mixture over vegetables. Cook about 6 minutes, or until almost set. As bottom of egg mixture sets, carefully lift edges with spatula and let uncooked egg run to the bottom of the pan.
Cook, covered, about 2 minutes, or until top is set but shiny. Sprinkle with cheese. Cook covered, about 1 minute, or until cheese melts. Tip: For browned top on frittata, place under broiler about 1 minute, or until cheese is browned and bubbly.