If using frozen shrimp, thaw them completely and pat dry with paper towels. Check that the shrimp are peeled and deveined, leaving the tails on if desired for a classic skewer presentation.
In a large mixing bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, paprika, garlic powder, salt, black pepper, and red pepper flakes, if using. Mix until the seasonings are evenly distributed.
Add the shrimp to the bowl and toss until each piece is coated. Cover and refrigerate for 20 minutes. Avoid marinating for too long because the lemon juice can change the shrimp's texture.
If using wooden skewers, soak them in water for at least 30 minutes to reduce burning. Preheat the grill to medium-high heat, approximately 400°F, and lightly oil the grates to prevent sticking.
Thread 4–5 shrimp onto each skewer, piercing each shrimp through both the thick end and the tail end so it lies relatively flat. This helps the shrimp cook evenly and makes flipping easier.
Place the skewers on the hot grill and cook for 2–3 minutes per side, until the shrimp turn pink and opaque and are cooked through. Avoid overcooking, as shrimp can quickly become tough and rubbery.
Transfer the shrimp to a serving platter and sprinkle with fresh parsley. Serve immediately with lemon wedges and, if desired, a little melted butter for dipping.
