Place the red peppers on their sides on a baking tray; cook under the grill, rotating until all sides have blackened. Remove and place inside a brown paper bag (or in a bowl covered with clingfilm) for about 10-15 minutes.
Carefully peel off the skin of the peppers and remove the seeds inside.
Slice the peppers lengthways and place in a bowl. Toss with olive oil and oregano. Season with salt.