Beckford brought up the ton with a stunning winner in his side's 2-1 victory over Wolverhampton Wanderers.
Grayson believes that the striker is happy at the club and that this is having a direct impact on his performances on the field.
"It was a spectacular way to bring up his 100th goal," said Grayson.
"He is enjoying life again and you can see that in his attitude on the pitch and in training. He feels a big part of this club."
Beckford's 100 league goals have come in 224 games for six different clubs.