Parker was the boss from the start pushing the visitor from West Virginian back with jarring jabs and right hands.
In the second round, Parker hurt Pettaway with a straight right to the body and was cracking him late in the round.
Pettaway came forward trying to make a fight of it in the third but was down from body shots with thirty seconds left in the round and was in trouble at the bell.
A four punch salvo punctuated by a right hand through the gloves had a cornered Pettaway down early in the fourth. He rose as referee John Conway reached the ten count.
Twenty three year old Parker moved to 13-0, 11 KOS. Pettaway, 34, dropped to 17-2, 10 KOS.
Parker is now due to go into camp with Wladamir Klitschko.
Heavyweight novelty “Brown Butterbean” David Letele scored a first round stoppage of Finau Maka. A short left hook inside dropped Maka and he was down a second time shortly after just 88 seconds.
A classy super middleweight six rounder was spoilt by a bad decision when Australian based Nigerian Friday Nwaiwu ( 3-5-1, 0 KO) had to settle for a split draw with former New Zealand Amateur Team Captain Joe Blackbourn (7-0-1, 7 Kos).
In his first bout since November 2012, Nwaiwu, picked Blackbourn apart for most of the contest, countering with quality punches in each round. A left hook knocked the NZ number one rated Blackbourn’s mouthguard out in the fourth. Blackbourn had a nice was never able to establish any momentum.
Scores 59-55 (Nwaiwu), 59-55 (Blackbourn) and 57-57. My score 59-55 Nwaiwu.
In an entertaining clash gun New Zealand amateur Bowyn Morgan (2-0, 1 KO) unanimously outscored a tough Ivana Seau (1-2, 1 KO) over six heats at middleweight.
Switch hitting Morgan, 33, won clearly, continually backing Seau up but made harder work of it than he needed, failing to cut the ring and neglecting to jab his way in, trying too hard to land big shots.
Parker training partner Izu Ugonoh (11-0, 9 Kos) scored a second round knockout of substitute Thomas Peato (2-3, 1 KO).
Polish number 6 heavyweight Ugonoh worked behind a stiff jab in the first round and landed solid right hands to the heart.
A perfectly placed left rip ended it.