Prepare the couscous according to packet instructions.
Heat the olive oil in a large frying pan over medium high heat. Add the garlic, tomatoes and red pepper. Once the tomatoes have softened, after about 3 minutes, add the prawns and stir to combine. Season with salt, pepper and oregano. Cook until the prawns are done and bright pink in colour, about 5 minutes.
Take off the heat and add the couscous, parsley and lemon. Toss to combine and then season more, if necessary. Enjoy warm, or it's also nice chilled the next day!