Bring a large pot of salted water to a rolling boil over high heat. Add the orzo and cook according to package instructions, typically 8-10 minutes, until al dente. Drain and rinse under cold water.

In a large mixing bowl, combine the diced red bell pepper, diced orange bell pepper, diced red onion, diced cucumber, corn, halved cherry tomatoes, chopped fresh basil, and sliced green onions. Toss gently until mixed.

In a small bowl, whisk together olive oil, lemon juice and zest, Dijon mustard, minced garlic, salt, and pepper until well-combined and emulsified.

Add the cooled orzo to the vegetable mixture. Drizzle the dressing over the top and toss gently to coat the ingredients evenly.

Serve immediately or refrigerate for 30 minutes to let the flavors meld. Top with freshly grated parmesan cheese before serving, if desired.