At the end, when the car is leaving the prison, the grass around is violently shaking revealing the helicopter carrying the camera.
Brubaker takes the (hot?) TV-Dinner out of the oven with his bare hands and carries it casually to the dining room table.
Yaphet Kotto looks through the 1/3 open blinds and watches Redford test the electric 'torture' box on himself.... But immediately before & after, when he's in the office talking w/ Redford, the blinds on both sides of the door are totally closed.
As Warden Renfro leaves, he tells Brubaker, "Smartest thing you ever did was come in here incognizant; dumbest was steppin' forward." The term is "incogNITO", which means unknown or unrecognizable. "Incognizant" means unknowledgeable or ignorant.
In a restaurant scene, a Conn's Potato Chip sales display can be seen. Conn's are only made and sold in Ohio, not Arkansas.
The movie supposedly takes place in Arkansas (although this is never explicitly stated, it is clearly indicated to be in the South, and likely near Texas and Louisiana). However, on the vehicles you can clearly see the OHIO license plates displayed. The movie was filmed about 3 miles west of Junction City, Ohio.
When Brubaker is eating a '70s-style TV dinner, multiple items change position/orientation in successive cuts. Specifically, the Tar-Tar sauce jar (closed/opened) and the bag of vegetables (changes position).
When Brubaker & another prisoner are taken to a local restaurant to drop off a steer; the guard drinks a beer which changes position in his hand after the camera goes back to the store owner for less than a second or two.