The 33-year-old actress, who first appeared on screen at age 8 in "ET: The Extra-Terrestrial," said "I'm able to make this incredible donation, this has changed my life, but I encourage everyone to give."
Having worked with WFP since 2005, she became an "Ambassador Against Hunger" in May 2007 and has devoted her time to brining attention to the damaging effects of hunger.
She added, "Children have such a capacity to learn when they're nourished."
Barrymore has been to Kenya twice to work hands on with the organization and has raised funds through a celebrity auction of her own photos. She has also discussed WFP's work on television shows and in magazine interviews.
During the show, Barrymore received a call from friend and "Charlie's Angel's" castmate, Cameron Diaz.
"I'm just so proud of Drew. I'm so proud of this information that she's giving the world and Oprah, you allowing to have her there and put it on. It's unprecedented - where we're at in the world right now, learning about how our children are living in the world is devastating and the truth that is being spoken there is so important for people to hear and I'm just so proud of you, Drew, for doing this and informing people," Diaz said.
Barrymore stressed the importance of local actions with a global mindset, which for Americans can mean donating 25 cents a day to WFP through their Fill The Cup campaign.
"Isn't it crazy in a world where we have so much abundance, and I mean everybody in this country compared to the rest of the world is living in abundance, but isn't it crazy that people are still dying because they can't get enough to eat?" she said.
The Rome-based agency has an annual budget of about $3 billion, but it said it needs $500 million more this year than it anticipated to help feed the world's poor because of the rising food and energy prices.