Ephraim has found himself out of favour at Rangers as he has appeared in just two first-team matches this season, including the 2-0 Carling Cup loss to Rochdale.
The 23-year-old winger has made 71 appearances and scored six goals for QPR since joining them in 2007.
A deal for the player could be sealed as early as next week.
Cotterill will watch his new Forest side from the stands on Saturday as they travel to Coventry.
The 47-year-old will then officially take charge of first-team affairs for the home match against Middlesbrough on Tuesday, October 18.