Harewood has had to endure a frustrating start to his Villa career and been down the pecking order behind Gabriel Agbonlahor and John Carew.
Reo-Coker said: "Marlon seems reborn. It is the same Marlon that was at Nottingham Forest - bullying players - and the hunger and appetite is there.
"It's taken him a while to settle and he's got that hunger back.
"It's been difficult for Marlon to go from first team regular at West Ham to a substitute at Villa - with a cameo appearance here and there.
"But he has made a big impact as a substitute. I am sure he will go from strength to strength now."