Immediately add the shrimp. Stir constantly. Add the oregano, a generous pinch of salt, and a generous amount of freshly ground pepper. Be sure that the garlic does not burn. As the shrimp turn pink,(2 to 3 min.), add the lemon juice. Stir thoroughly. Cook only until the shrimp are pink and resilient to the touch, no more than 3 to 4 minutes. If overcooked, shrimp are tough.
Note: Provide guests with large bibs or wet towels. Use either large (16 to 20 per lb.) or medium (25 to 32 per lb.) shrimp.