After blowing big leads against Carolina and Tampa Bay, the Bears hung on.
The Eagles (2-2) threatened to take the lead after a 41-yard field goal by Robbie Gould made it a four-point game with 10:28 remaining, launching a 75-yard drive that took nearly seven minutes.
Problem was they needed 76.
They had second down at the 1 when Tony Hunt got tackled for no gain by Kevin Payne and Mike Brown. A leaping Buckhalter, filling in for injured Pro Bowl running back Brian Westbrook, then got stopped a few inches short by Adewale Ogunleye on third down. He tried to go through the line on fourth down, only to be met by Alex Brown.
The Bears took over and Matt Forte sealed it with a 10-yard run that gave the Bears (2-2) a first down on their 17.
In the first half, Chicago's Kyle Orton picked apart a defense that sacked Ben Roethlisberger eight times while beating Pittsburgh last week, but he was shaky in the second.
He was 18-of-34 with 199 yards and a career-high three touchdowns - all in the first half, as the Bears built a 21-14 lead. Orton threw for just 25 yards in the second half as the Bears nearly gave away the game.
Chicago blew a big opportunity after Payne returned an interception 49 yards to the Eagles 11 in the third, only to have Orton get intercepted in the end zone by Quintin Mikell. After Philadelphia's David Akers booted a 47-yard field-goal attempt off the right upright four minutes into the quarter, Orton immediately coughed up the ball on a sack by Trent Cole.
The Eagles' Omar Gaither recovered, leading to a 24-yard field goal by Akers that pulled Philadelphia within 21-17. Another fumble by Orton led to a 31-yarder by Akers to make it a one-point game less than two minutes into the fourth.
But the Bears got that big stand near the end and let out a big sigh of relief.
They'll take this after blowing a 14-point lead in a 20-17 loss at Carlina, then seeing a 10-point advantage disappear in the closing minutes of regulation in a 27-24 overtime loss to Tampa Bay last week.
Donovan McNabb had another good game for the Eagles, passing for 262 yards and a touchdown and interception, but they got little from the running game with Westbrook nursing an ankle injury.
Buckhalter had 16 carries for 66 yards, and DeSean Jackson added 35. He also caught five passes for 71 yards and a touchdown, while Reggie Brown had six catches for 79.