Prosecutors said Peacock entered the plea Monday in Washington County Circuit Court, where he also was sentenced to a year of supervised probation.
Peacock was arrested March 16 on a felony theft charge for allegedly taking a fellow student's debit card and using it to buy $35 worth of gas.
Former Arkansas coach Bobby Petrino suspended Peacock indefinitely, but he was reinstated prior to Petrino's firing. The 6-foot-4, 305-pound senior was listed as a first-team tackle on the Razorbacks' spring depth chart and is an important piece to Arkansas' offensive line. Peacock played in all 13 of Arkansas' games last year and started the final nine games.
Arkansas interim coach John L. Smith released a statement concerning Peacock:
"I met with Jason Peacock when I arrived on the job and expressed my expectation for him to fulfill his obligations in order to resolve his situation. We have high standards for our student-athletes and now that the legal process has taken its course, we will review Jason's status with the program."
Prosecutors say Peacock is to report to jail within 30 days.