Howlett and Earls are in contention to face the defending champions along with Ronan O'Gara, David Wallace, Felix Jones and James Coughlan, who all sat out the 13-6 victory over the Scarlets.
The injured Johne Murphy (eye), Declan Cusack (shoulder) and Sam Tuitupou (calf) are among the absentees for the Magners League leaders.
Munster hosted an open training session at Cork IT in brilliant sunshine on Thursday. Included in the large crowd that turned out was a 60-strong French contingent who are over on tour from Gap.
Munster captain Paul O'Connell, who is nursing an ankle injury, was also involved in the session. He was confined to individual work with physiotherapist Neil Tucker.
"What's in it for us? We're anxious to perform, we're a competitive squad and we're very lucky at the minute to have the vast majority of our players available for selection.
"In the past, maybe the selection of our team was cut and dried, but it's nowhere near that nowadays.
I know we're going to finish top of the league, nothing will change that now, but there is a lot to play for. We need to perform, especially against the Ospreys, because potentially we could be meeting them again this season."
MUNSTER Squad (v Ospreys) - Backs (11): Felix Jones, Scott Deasy, Doug Howlett, Simon Zebo, Lifeimi Mafi, Paul Warwick, Keith Earls, Danny Barnes, Ronan O'Gara, Peter Stringer, Conor Murray.
Forwards (16): Marcus Horan, Wian du Preez, Darragh Hurley, John Hayes, Tony Buckley, Stephen Archer, Damien Varley, Mike Sherry, Ian Nagle, Donncha O'Callaghan, Donnacha Ryan, Alan Quinlan, David Wallace, Tommy O'Donnell, Niall Ronan, James Coughlan.