Preheat your oven to 200°C (400°F) and line a large baking sheet with parchment paper or foil.
Prepare the glaze: In a small bowl, whisk together the balsamic vinegar, olive oil, minced garlic, brown sugar, Italian seasoning, salt, and black pepper.
Roast the veggies: Toss the baby potatoes, broccoli, zucchini, and bell pepper with half of the balsamic mixture. Spread them evenly onto the prepared sheet pan and roast for 20 minutes, until the potatoes begin to soften.
Add the steak: Remove the pan from the oven, push the vegetables to the sides, and place the cubed steak bites onto the sheet pan. Drizzle the remaining balsamic mixture over the steak bites.
Finish roasting: Return the sheet pan to the oven and bake for an additional 10 to 12 minutes, or until the vegetables are tender and caramelized and the steak is cooked to your liking.
Serve: Garnish with fresh chopped parsley and serve warm directly from the sheet pan.