Heat oil in a large nonstick skillet over medium-high heat. Add bell peppers and onion; sauté 8 minutes or until tender. Stir in vinegar, sugar, oregano, and garlic powder.
Place the toast slices on a baking sheet. Top each toast slice with 3 ounces roast beef, 6 tablespoons Cheese Sauce, and 3/4 cup bell pepper mixture. Broil for 1 minute or until the sandwiches are thoroughly heated. Sprinkle the sandwiches with chopped parsley.
This has as much relationship to a Philly cheese steak as cheese wiz has to actual cheese. (Which I might add is the authentic dairy product used on the real thing!) But it is tasty. Roast the peppers very dark for the best flavor.
The cheese sauce is going to be watery; very watery.
Adding water, which comprises 80+ percent of low fat/no fat milk, to flour and
expect to make a roux, béchamel or mornay sauce is like mixing sand and water and
expecting to make mortar or concrete. Putting whole peppercorns into anything that cooks
for only 5 minutes, is useless. Use white pepper instead. And then there’s
balsamic vinegar and sugar. I’m not sure about that. And I don’t know if I want
to trash $10 a lb. roast beef to find out that it’s really terrible.