Tries from wing Keith Earls and skipper Peter O'Mahony, plus ten points from the boot of fly-half Ian Keatley, secured Munster top spot in Pool 6.
But Penney reserved special praise for his captain, who started the Lions' first Test against Australia this summer before suffering a broken arm in the closing stages.
"Paul is just such an amazing character, and at this level of the game you wouldn't want anyone else out there, really, guarding your ship," Penney told the Irish Times.
Even Gloucester boss Phil Davies couldn't resist lauding the giant forward. He said: "Paul O'Connell is phenomenal.
"There are certain characters in teams that have a huge influence and effect. It is not just his ability as a rugby player, it's how he galvanises the team, and his sheer presence is a huge factor for Munster."