Preheat the oven to 400°F. Line a large, rimmed sheet pan with parchment or cooking spray for easier clean up. Set aside.
In a small saucepan, combine the soy sauce, brown sugar, rice vinegar, sesame oil, honey, cornstarch, ginger, garlic powder, and red pepper flakes. Set over medium-high heat. Bring to a boil, whisking frequently, then reduce heat to medium and let it bubble for about 5 minutes, until the sauce is thick enough to visibly coat the back of a spoon. Set aside to cool briefly.
1/2 cup low-sodium soy sauce, 1/4 cup packed light brown sugar, 2 Tablespoons rice vinegar, 1 Tablespoon toasted sesame oil, 1 Tablespoon honey, 1 teaspoon cornstarch, 3/4 teaspoon ground ginger, 1/2 teaspoon garlic powder, 1/8 teaspoon red pepper flakes
While the sauce bubbles, chop the veggies. Toss them all—broccoli, bell peppers, carrots, and onion—on half of the sheet pan.
2 cups broccoli florets, 1 or 2 medium bell peppers, 2-3 medium carrots, 1/2 medium yellow or red onion
Drizzle veggies with olive oil, sprinkle with salt and pepper, and toss to combine. Place in the oven for a couple of minutes while you slice the chicken and the sauce continues to cool.
2 teaspoons olive oil, kosher salt and black pepper
When the chicken is prepped, remove pan from the oven and add meat to the other half of the sheet pan. Sprinkle with a big pinch each of salt and pepper, then pour about 1/3 cup of the teriyaki sauce over the chicken. Spread the pieces out into a single layer, leaving space between them if possible and turning to coat both sides in the sauce.
2-3 large boneless, skinless chicken thighs or breasts
Return to the oven and bake for about 15 minutes, until the veggies are tender and the chicken reaches 165°F.
Remove from the oven and drizzle everything with the remaining teriyaki sauce, either on the pan, in a serving dish, or in individual bowls. Garnish with sesame seeds and sliced green onions, if desired, and serve over rice or noodles. Enjoy!