Begin by bringing a large pot of salted water to a rolling boil. Add the orzo and cook according to the package instructions, typically around 8-10 minutes, until al dente. Once cooked, drain the orzo in a colander and give it a quick rinse under cold water to stop the cooking process. Set it aside to cool while you prepare the vegetables.

In a spacious mixing bowl, combine the diced red and orange bell peppers, finely chopped red onion, diced cucumber, sweet corn, and halved tomatoes. Toss in the fresh basil leaves and sliced green onions for added flavor. Mix gently to ensure all vegetables are evenly distributed, creating a colorful and vibrant base for your Summer Orzo Pasta Salad.

In a small bowl, whisk together the olive oil, fresh lemon juice, zest, Dijon mustard, minced garlic, and a generous pinch of salt and pepper. Whisk until the mixture is smooth and emulsified, about 1-2 minutes.

Add the cooled orzo to the bowl with the prepared vegetables. Drizzle the lemon vinaigrette over the orzo and vegetables, then toss gently to ensure everything is well coated.

To serve, transfer the salad into a large serving bowl or individual plates, and top with freshly grated Parmesan cheese if desired. This dish can be enjoyed immediately or covered and stored in the refrigerator for up to four days.