Pouncey will become the NFL's highest-paid center at $11 million per year over three years, according to ESPN's Adam Schefter.
A source confirms Foster is signing for two years and is worth $8.25 million.
Foster and Pouncey have started along the Steelers' line for the past nine seasons. Pouncey, a first-round pick in 2010, has made three straight Pro Bowls. Foster is an undrafted free agent from 2009 who keeps producing.
Keeping the line together sets the stage for a mega-deal for quarterback Ben Roethlisberger, who is close with his linemen.
As insurance, the team also placed a second-round tender on guard B.J. Finney, a restricted free agent. The tender is worth $3.095 million.
The Steelers are still talking with teams about trading Brown, and a deal could happen as early as Friday.