Preheat the oven to 400°F (200°C). Line a large sheet pan with parchment paper or lightly grease it.
In a large bowl, combine ground beef, panko breadcrumbs, chopped green onions, egg, minced garlic, grated ginger, and 2 tablespoons of soy sauce. Mix until just combined.
Form the mixture into 1 1/2-inch meatballs and place them evenly spaced on one side of the prepared sheet pan.
In a separate bowl, toss the red bell pepper pieces, zucchini slices, broccoli florets, and carrot slices with olive oil and the remaining 2 tablespoons of soy sauce. Spread the vegetables evenly on the other side of the sheet pan.
Bake the meatballs and vegetables for 20 minutes, or until the meatballs are cooked through and vegetables are tender.
While baking, prepare the teriyaki sauce by combining honey, rice vinegar, sesame oil, and the remaining 1/4 cup soy sauce in a small saucepan over medium heat.
In a small bowl, whisk cornstarch and water until smooth, then slowly add to the saucepan, stirring constantly until the sauce thickens, about 2-3 minutes. Remove from heat.
Remove the sheet pan from the oven. Brush the meatballs and vegetables generously with the teriyaki sauce.
Return the sheet pan to the oven and bake for an additional 5 minutes to glaze the meatballs and vegetables.
Remove from oven and sprinkle toasted sesame seeds over the meatballs and vegetables before serving.