Put the olive oil, garlic and chile flakes in a small skillet. Turn the heat to low and let the mixture heat for about 10 minutes; the oil should just barely simmer around the garlic in the last few minutes. Remove from the heat and cool slightly. Transfer to a blender, add the 1 tablespoon oregano and some salt and pepper, and blend until the garlic and oregano are finely chopped. Set aside half of the chile-garlic oil for serving.
Heat the grill to high. Thread the shrimp onto skewers, about 4 or 5 shrimp per skewer, threading so that the skewers goes through the tail and thick end of each shrimp. Brush the shrimp with some of the chile-garlic oil and season with salt and pepper. Grill until lightly golden brown on both sides and opaque, 1 to 1 1/2 minutes per side. Transfer the skewers to a platter and immediately drizzle with some of the reserved chile-garlic oil (not the oil you used for brushing the raw shrimp). Garnish with oregano, and serve with more of the reserved oil.