Cook linguine according to package directions; drain. Return linguine to hot pan; cover and keep warm.
Meanwhile, drain clams, reserving juice from one of the cans (you should have about 1/2 cup). Add enough half-and-half to the reserved juice to measure 2-1/2 cups clam liquid. Set clams and clam liquid aside.
In a medium saucepan cook onion and garlic in hot butter over medium heat until onion is tender. Stir in flour, dried oregano (if using), salt, and pepper. Gradually stir in clam liquid. Cook and stir until thickened and bubbly. Cook and stir for 1 minute more.
Stir in drained clams, snipped oregano (if using), parsley, and wine; heat through. Serve clam mixture over warm linguine. Sprinkle with cheese and, if desired, additional fresh oregano.