Place potato slices and enough water to cover in a large saucepan. Over high heat, heat to boiling; reduce heat to low. Cook potatoes 5 minutes or until almost tender. Drain well.
Meanwhile, in 10-inch skillet over medium heat, in hot oil, cook onion and pepper until tender-crisp, about 5 minutes, stirring occasionally.
In blended or food processor, blend evaporated milk, eggs, flour, salt and pepper until blended and smooth.
Preheat oven to 350*F. Grease 13-by-9-inch baking dish or casserole. Set aside ½ cup queso blanco. Place a layer of sliced potatoes in baking dish; top with a layer of sautéed vegetable mixture, a layer of shredded cheese and a sprinkle of Cotija cheese. Repeat layering until potatoes, vegetables and cheese are used. Pour egg mixture over potatoes. Sprinkle with reserved queso blanco. Cover dish with foil.
Bake 30 minutes. Uncover and bake 15 minutes longer or until golden brown on top.