Toss the zucchini, bell peppers, onion, and garlic with the olive oil, salt, and pepper on a large sheet pan. Roast for 40 minutes, until golden brown, turning once with a spatula.
While the veggies are roasting, cook the orzo in boiling salted water for 7 to 9 minutes, until tender. Drain and transfer orzo to a large serving bowl. When the veggies are done, add them to the pasta making sure to add all the liquid and seasoning, too.
For the dressing, combine the lemon juice, olive oil, salt, and pepper and pour on the pasta and vegetables. I like to make the dressing ahead of time and add it while the orzo is still warm which helps the dressing flavors infuse into the orzo. Let pasta cool to room temperature, and then add the scallions, pignolis, feta, and basil.
Taste and season with extra salt, pepper and lemon juice if needed.
Serve at room temperature. This salad can also be made a day ahead and stored in the fridge. Bring to room temperature before serving.
Notes
Adapted slightly from Ina Garten, Barefoot Contessa, Barefoot Contessa Parties!