General Mills, which also sells the Old El Paso and Betty Crocker brands, was the only one of the top 10 food and drink companies in the world that had not improved its sourcing policies, Oxfam said.
The charity's "Behind the Brands" scorecard measures the sourcing policies of the 10 biggest food and drink companies, looking at transparency, women and other workers, farmers, land, water and climate.
And Oxfam said that while progress had been made by some of the companies on land, women's rights and carbon emissions and some leading companies had made "major strides", overall the "big 10" had moved too slowly as a group.
It said that before the campaign launched a year ago, none of the 10 companies had policies to ensure their ingredients were not grown on land that had been taken from communities.
Now, six had policies to help ensure their suppliers were not involved in land grabs, seven had committed to improving conditions for women affected by their operations and eight had improved their policies on climate, mainly through better disclosing their emissions and risks related to climate change.
Oxfam's campaigns and policy director, Ben Phillips, said: "Consumer power and investors are pushing most of the top 10 food and drink companies in the right direction and we are beginning to see what this can mean for poor and vulnerable people.
"These companies, with so much power and influence, can do so much more and while some are showing leadership, others are clinging to a business model that is outdated and fails to respect human rights.
"Pressure from consumers is what pushed companies to be more responsible and so much more is possible if people continue to add their voice."
The top three performers - Nestle, Unilever and Coca-Cola - all improved their scores by the biggest margins, Oxfam said.
The rankings as listed by Oxfam for this year, showing a total score adding up points relating to land, women, farmers, workers, climate, transparency and water, are:
1. Nestle 45/70
2. Unilever 44/70
3. Coca-Cola 38/70
4. Mondelez 23/70
4. PepsiCo 23/70
6. Danone 22/70
6. Mars 22/70
8. Kellogg's 20/70
9. Associated British Foods 19/70
10. General Mills 15/70