Brown the turkey sausage: Heat a large skillet or Dutch oven over medium-high heat. Add 1 pound turkey sausage and cook, breaking it apart with a spoon, until browned and cooked through, about 5–7 minutes. Transfer the sausage to a plate and set aside.
Cook the aromatics: Reduce the heat to medium. Add ½ cup yellow onion, diced, to the same skillet and cook for 2–3 minutes, scraping up any browned bits from the bottom of the pan. Add 3 garlic cloves, minced, and cook for about 30 seconds, until fragrant.
Build the orzo: Stir in 1 ½ cup orzo and ½ teaspoon Italian seasoning and cook for about 1 minute. Add 3 cups broth and stir.
Cook the orzo: Bring the mixture to a boil, then reduce the heat to a simmer. Cook uncovered for 8–10 minutes, stirring occasionally, until the orzo is nearly tender and most of the broth has been absorbed.
Add 1 cup frozen peas, and 1 cup frozen corn and cook for another 2–3 minutes, until the vegetables are heated.
Then stir in the cooked turkey sausage, 1 (15-ounce) can cannellini beans, drained and rinsed and ½ cup pesto and stir. If the orzo becomes too thick before it is tender, add a splash of chicken broth.
Finish and serve: Remove from heat and let the orzo sit for 2–3 minutes. Serve with ½ lemon, cut into wedges, fresh basil, and Parmesan cheese, if desired. Add extra pesto on top for even more flavor.