Preheat the oven: Preheat the oven to 400° and line a rimmed baking sheet with parchment paper.
Chop the beef: Cut the top sirloin into large chunks, about 2" X 2".
2 pounds top sirloin
Make the marinade: In a small bowl or measuring cup, whisk together soy sauce, honey, brown sugar, rice vinegar, garlic powder, and ground ginger until combined. Pour half into a large zip-top bag and reserve the remaining marinade (about ¾ cup).
½ cup soy sauce, ¼ cup honey, 3 tablespoons brown sugar, 2 tablespoons rice vinegar, ½ teaspoon garlic powder, ½ teaspoon ground ginger
Marinate the beef: Add the beef chunks to the bag and turn to coat. Refrigerate for 30 minutes, turning it over about halfway.
Prep the vegetables and pineapple: Cut the onion into fourths, the bell pepper into eighths, the zucchini into half-inch slices, and and pineapple into large chunks.
1 red onion, 8 pieces pineapple cut into 1" chunks, 8 fresh mushrooms, 8 pieces zucchini, 1 bell pepper
Assemble the kabobs: Thread onto skewers in this order: beef, zucchini, beef, onion, whole mushroom, green pepper, then pineapple chunks. Repeat once more.
Bake: Place the skewers on a rimmed baking sheet and bake at 400° F for 22–26 minutes, turning halfway through.
Make the sauce: While the skewers bake, heat the reserved marinade in a small saucepan over medium heat until hot. In a small bowl, whisk together 1 tablespoon water and 1 tablespoon cornstarch to make a slurry. Stir it into the sauce and cook for 3–5 minutes, or until thickened.
1 tablsepoon corn starch, 1 tablespoon water