He will be partnered in the second row by Jonathan Pendlebury, who will make his competitive debut, in one of six changes made by head coach Dean Ryan following last Saturday's Powergen Cup elimination against Bath.
As well as a complete change at lock because both Mark Cornwell and Adam Eustace are rested, prop Patrice Collazo returns in the front row in place of Nick Wood and Jake Boer returns after an ankle injury in place of Andy Hazell on the openside, who is ruled out because of a knee complaint.
James Forrester begins at number eight which means a switch to the blindside for Adam Balding in place of Peter Buxton, who moves to the bench.
In the backs, the increased physicality of Terry Fanolua is preferred to the running capabilities of Anthony Allen in the centre alongside Mike Tindall, while Marcel Garvey returns on the wing in place of James Bailey, who is not registered in Gloucester's European squad and has been called up by the England Sevens squad.
England's James Simpson-Daniel is ruled out for the second week running because of a hip injury.
Ryan has named nine travelling replacements and two will drop out of the squad tomorrow.
But it is the return of Brown in the heartbeat of the Gloucester forward effort that is perhaps key in Toulon.
"I am just really pleased the rehab has gone so well," Brown told www.gloucesterrugby.co.uk. "There was a very real possibility - it was a 50-50 situation - that I may require an operation but we opted for the natural process and it has paid off.
"My initial aim was to be fit for the Wasps game on Boxing Day but if I can get 40 minutes here and 40 minutes there, that will stand me in good stead.
"Dean [Ryan] has been very relaxed about the situation and has not put any extra pressure on me to get back because he wanted to make sure I was right.
"Nothing replicates the contact situation you face in a match but I am confident everything will be okay.
"It may sound a strange thing to say but we expect Toulon to be typically French in their approach. They will be physical, have a big drive and a good line-out and solid scrum. But to be honest, it does not matter what they do.
"We are simply concentrating on what we are good at and ensuring we produce a performance. If we can do that, then I am confident we can get the result we need."
Gloucester are top of their pool with victories against Bayonne and Bucuresti and it is likely that tomorrow's encounter may decide the outcome of the group.
Toulon travel to Kingsholm a week tomorrow before Gloucester complete their group games at home to Bayonne and away to Bucucresti.
GLOUCESTER (v Toulon, away, tomorrow): Olly Morgan, Marcel Garvey, Terry Fanolua, Mike Tindall, Mark Foster, Ludovic Mercier, Peter Richards; Patrice Collazo, Mefin Davies, Phil Vickery (capt), Jonathan Pendlebury, Alex Brown, Adam Balding, Jake Boer, James Forrester. Reps: Rob Elloway, Gary Powell, Nick Wood, Quinton Davids, Peter Buxton, Duncan McRae, Anthony Allen, Jon Goodridge.