1Mix potatoes, corn and onion salt. Spray 10-inch nonstick skillet with cooking spray; heat over medium heat. Pack potato mixture firmly into skillet, leaving 1/2-inch space around edge. Reduce heat to medium-low. Cook uncovered about 10 minutes or until bottom starts to brown.
2Meanwhile, mix eggs, milk, marjoram and pepper sauce. Pour egg mixture over potato mixture. Cook uncovered over medium-low heat. As mixture begins to set on bottom and side, gently lift cooked portions with spatula so that thin, uncooked portion can flow to bottom. Avoid constant stirring. Cook about 5 minutes or until eggs are thickened throughout but still moist. Sprinkle with cheese.
3Reduce heat to low. Cover and cook about 10 minutes or until center is set and cheese is bubbly. Loosen bottom of frittata with spatula. Cut frittata into 4 wedges.