The 24-year old former Leeds United man netted 24th, 48th, 82nd and 84th minutes as the Bess completely dominated proceedings at Griffin Park.
Grella, who initially joined Brentford on an emergency loan from Leeds in August, admits it was nice to get amongst the goals for his new club but stressed the importance of qualifying for the sectional semi-finals.
"It's always good just to play and to be fit and to score. I'm pleased with the goals and that the team won," Grella said.
"I pride myself on scoring with both feet. I thought I had three pretty good headers today.
"We put on quite a show for the fans, especially at home.
"I came here to play games and to help the team and help the team in any way I can," he added.
"I've come here to play and every player here wants to play games and I'm disappointed if I'm not playing but I have to respect the managers decision."