At present, the 43-year-old is only in charge at Ibrox until the end of the season with calls growing for a new manager to be installed.
Reading are on the lookout for a new head coach after Jaap Stam departed the Championship side early on Wednesday and could turn to their former player.
The Scottish international spent 11 years with the Berkshire club, including a lengthy spell as captain.
He is currently 14/1 to SkyBet to take over, which makes him the fourth leading candidate in the market.
Paul Clement is the runaway favourite at present, priced at 1/10, while ex-Rangers boss Mark Warburton is joint-second on the list with Steve McClaren at 12/1.