Cook orzo according to package directions. Drain well. Return orzo to hot saucepan.
Meanwhile, cut lemon in half; finely shred peel from half of the lemon. Cut remaining lemon half into wedges.
Add spinach and lemon peel to orzo in saucepan; toss to mix. Season to taste with salt and ground black pepper. Divide orzo mixture among four dinner plates. Arrange chicken on top of orzo mixture. Serve with lemon wedges.