Everton have failed to live up expectations so far this season.
The quartet are all over the age of 30, and Townsend feels that they are reaching the twilight of their careers.
The former Republic of Ireland international admits that they all still have a part to play for now, but he would be looking to move two of them on in the summer.
“I see Everton as a team in transition,” Townsend said. “The likes of Tim Howard, Phil Jagielka, Leon Osman and Gareth Barry - none of them are getting any better now.
“They’ve all been very good players, and are still offering something to the team, but they’re not getting any better. I think they have a lot of experience boys, where now Roberto has to be brave and freshen it up. I think they’ve got five or six older ones, and I’d cut it down to two or three.”
Howard looks the most likely player to leave Everton this summer, as he has had a disappointing season.
The American international stopper has put in a series of erratic performances, and now has lost his place in goal to Joel Robles.
Osman also could move on, as he has struggled for first-team appearances throughout the campaign.
The departures of Barry or Jagielka would be more surprising, as the pair are still playing key roles.
Barry and Jagielka provide the experience in what is a young Everton squad, and still are regularly selected in Roberto Martinez’s starting line-up.