Start a charcoal or gas grill or heat a broiler; fire should be quite hot and rack about 3 inches from heat source. If you like, thread fish onto skewers (it is easier to turn fish if you use two skewers per kebab). Brush fish with a little olive oil and sprinkle it with salt and pepper. In a bowl, combine garlic with remaining oil, salt, pepper and oregano (or combine whole garlic cloves and these ingredients in container of a small food processor). Mixture should be nearly smooth; stir in lemon juice and set aside. Grill or broil fish, turning as each side browns, at least 2 minutes a side. When a thin-bladed knife inserted into center of chunk meets almost no resistance, it's done. Brush with garlic sauce, garnish with parsley if you like, and serve.