Season both sides of the sirloin steak with the salt and pepper. Set aside.
Heat the olive oil in a large skillet over medium high heat. Sear the steak on both sides, approximately 1 minute on each side until lightly browned. Remove to a plate and set aside.
If the skillet is dry, add 1 teaspoon of additional olive oil. Add the mushrooms, onion, red and green bell peppers to the skillet, sauteing for 3-4 minutes or until they start to soften. Add the garlic, sauteing for another 1-2 minutes.
Deglaze the pan with the white wine and stir in the crushed tomatoes, oregano and parsley. Reduce the heat to low.
Return the steak to the skillet, covering with sauce. Cook on each side for an additional 3 minutes (6 minutes total). Remove the steak to a cutting board to rest for 5 minutes.
Continue to simmer the sauce while the steak is resting, stirring in the balsamic vinegar.
Slice the sirloin against the grain and plate on dishes. Top with the simmering sauce and serve with bread.