McGrath's 61 in Australia's first innings of the first Gabba Test last week was the highest ever by an Australian No.11.
He featured in a 114-run last-wicket stand with fellow fast bowler Jason Gillespie, who remained unbeaten on 54 in Australia's first innings of 585.
McGrath's crowd-pleasing knock surpassed the previous best by an Australian No.11 -- 52 by Rodney Hogg against the West Indies in Georgetown in 1983-1984.
McGrath was on Thursday presented with a 10,000 Australian dollar (7,700 US) cheque from bat sponsor Sommers for an incentive in his contract rewarding him for a maiden Test half-century.
"I think they thought it was a pretty safe bet," McGrath said of the incentive.
"I think I will have to renegotiate a new incentive in my contract for a Test 100. But I don't think they will worry about that (happening)."
The much-publicised knock also earned the batting bunny a further 6,100 dollars for the McGrath Breast Cancer Foundation.
Through a deal with his major sponsor, New Loan, the charity receives 100 dollars per run and 200 dollars for each wicket of McGrath in Test cricket.