Strange, the first reserve, replaced David Drysdale, who pulled out with a neck injury. Strange was on the bus to the Arlandastad course when organizers told him to tee it up.
'I've never experienced anything like this before, and I'll remember it for the rest of my life,' said Strange, who had seven birdies and one bogey. 'There was a lot going on in my head.'
Swedish amateur Fredrik Qvicker and Sam Walker were one shot behind. Corey Pavin, Jeff Sluman and two-time Scandinavian Masters winner Jesper Parnevik shot 70. Defending champion Marc Warren and John Daly shot 72.
Strange, who had not practiced on the course because his clubs arrived late from his previous tournament in Scotland, opened with a birdie on his first hole. He is 117th on the Order of Merit and in danger of losing his card.