No, no, no, no, no. What's a lid doing on that? First, a bit of oil, then start the onions sauteing. After a few minutes, add the peppers and mushrooms and cook until the onions are just starting to turn brown. Crank the heat full blast, and add the fairly finely chopped steak. Cook rapidly for all of a minute or so until the steak is cooked through - need a large pan. Have a roll ready - light amount of mayo, then a layer of provolone cheese (acts as a heat shield for the whiners above). Then dump that meat on, toss in some mozzarella - just enough to hold everything together so it doesn't fall all over when eating, and toss into the oven to toast.
Steamed steak? Ick. May as well boil it.