Bring a 3-quart pot of water to boiling. Lightly salt water and add orzo. Cook, stirring occasionally for 9 minutes. Stir in peas and return to a boil; boil 1 minute, then drain.
Toss orzo and peas with butter and oregano, stirring until butter is melted. Stir in cheese, lemon juice, zest, salt and pepper. Serve warm.
Makes 6 servings.