Season both sides of each steak generously with the salt and black pepper; allow to rest for 10 to 15 minutes.
Heat the vegetable oil in a large sauté pan, over medium-high heat; add the garlic; when the garlic starts to shimmer, carefully place the steaks in the pan; cook the steaks individually if your pan won’t accommodate both steaks without touching.
Sear the steaks on each side for 7 minutes, or until the meat is dark brown on each side; transfer the steaks to a large sheet of parchment paper.
Add the bell peppers, onions and mushrooms to the pan and sauté for 5 minutes; tossing frequently.
When the onions are translucent and the mushrooms have browned, add the wine; cook for 2 minutes more.
Add the marinara sauce; bring to a simmer.
Place steak back in the pan, with sauce; cook for 2 minutes for medium-rare; longer for a different cooked temperature.
Transfer the steaks to a cutting board; let rest for 5 minutes.
If serving family style, slice the steaks on a diagonal and transfer to a warmed serving platter.
If serving individually, place each steak on a warmed plate.
Spoon the sauce over the steaks; sprinkle with the parsley and serve.
