Together with Martin Conway, G. S. Scriven and guides Ferdinand Imseng and Peter and M. Truffer he made the first ascent (in two and a half hours) of the west face of the Zinalrothorn in August 1878.
[5] With Albert Frederick Mummery and guides Alexander Burgener and Ferdinand Imseng he made the first ascent of the Dürrenhorn on 7 September 1879.
According to Penhall, his interest in finding a new way up the mountain had been kindled by Edward Whymper's account of the successful first ascent in 1865 in Scrambles amongst the Alps.
After a brief rest in Zermatt, Penhall returned to the Matterhorn, making the first ascent of its west face on 3 September 1879, a harder climb than the Zmutt ridge; his party reached the summit one hour after Mummery's.
[8] Penhall wrote an account of the west face climb in the Alpine Journal entitled 'The Matterhorn from the Zmutt Glacier'.