Wash and dry all produce. Bring a large pot of salted water to a boil. Finely chop parsley. Mince or grate garlic. Halve, peel, and finely chop onion. Halve tomatoes. Halve zucchini lengthwise, then slice into 1/4-inch-thick half-moons. Core and seed bell peppers, then thinly slice. Cut lemon into wedges. Slice sausage into 1/2-inch-thick rounds.

Heat a large drizzle of oil in a large pan over medium-high heat. Add sausage and cook until browned, 2-3 minutes per side. Remove from pan with a slotted spoon and set aside, keeping as much grease in pan as possible.

Heat another large drizzle of oil in same pan over medium heat. Add onion and zucchini. Cook, tossing, until softened, 5-6 minutes. Season with salt and pepper.

Once water is boiling, add orzo to pot. Cook, stirring occasionally, until al dente, 7-9 minutes. Carefully scoop out and reserve 1/2 cup pasta cooking water, then drain.

Add bell peppers and garlic to pan with zucchini. Cook, tossing, until bell peppers are softened, 2-4 minutes. Add tomatoes and cook until warmed through, 1-2 minutes. Season with salt and pepper.

Toss orzo and sausage into pan with veggie mixture. Add half the Parmesan, a squeeze of lemon juice, and a splash of pasta cooking water and stir to combine. Season with salt and pepper. Divide between plates, then garnish with parsley and remaining Parmesan.