Preheat the oven to 425 degrees F. Lightly grease a large sheet pan or line it with parchment paper.
In a small bowl, whisk together soy sauce, brown sugar, honey, garlic, ginger, and rice vinegar. In a separate small bowl, mix cornstarch and water, then stir it into the sauce.
Place the beef, broccoli, bell peppers, zucchini, carrots, and onion on the sheet pan. Drizzle with olive oil and toss gently to combine.
Pour about two-thirds of the teriyaki sauce over the beef and vegetables, then toss everything together so it is evenly coated.
Spread the mixture into an even layer. Bake for 18 to 22 minutes, stirring once halfway through, until the vegetables are tender and the beef is cooked through.
Drizzle the remaining sauce over the top and sprinkle with sesame seeds before serving.
Serve hot on its own or over rice. Store leftovers in the fridge for up to 3 days.
