But the 23-year-old refuses to take all the credit and revealed the try was the result of a lot of hard work and preparation on the training pitch.
"To be honest, it was more pleasing for me to finish off a team move," he told the South Wales Evening Post.
"The boys did really well to create the space. It was something we'd worked on throughout the week, so it was really good just to get on the end of a team play like that.
"A score like that doesn't happen unless everyone knows their roles and executes them, as the boys did at the Millennium Stadium."
With just two regular season games against Glasgow Warriors and Connacht remaining Ospreys sit fourth in the table.
And Grabham is pleased to see the team firing on all cylinders as the GUINNESS PRO12 play-offs draw ever closer.
"It is a young back division, but there's experience there as well, with Webby (Rhys Webb) and Biggs (Dan Biggar) driving standards, Josh Matavesi in midfield and Dan Evans at full-back," he added.
"When we filter in that bit of youth we blend well and work together. Each of us drives each other's standards, creating a competitive environment."
Follow us on Facebook, join the conversation on Twitter, sign up to our YouTube channel for extensive match highlights and sign up for our newsletter for regular updates on the GUINNESS PRO12
63x46.png){kind=logo}