This is the second such study of food items. The first study earlier this year had similar results and found that more than 30 oat-based foods contained the chemical.
Scientists with the EWG said the group found amounts that were more than what they "consider protective of children's health," CNN reported.
Manufacturers of the cereals say their products are safe.
Quaker officials say of the report that, "EWG report artificially creates a 'safe level' for glyphosate that is detached from those that have been established by responsible regulatory bodies in an effort to grab headlines," according to CNN.
General Mills officials responded with a statement to CNN, "The extremely low levels of pesticide residue cited in recent news reports is a tiny fraction of the amount the government allows."
But the EWG disagrees, saying glyphosate levels could be a cancer risk if consumed for a long period of time, CBS News reported.
The World Health Organization calls it a probable carcinogen, according to CBS.
But experts warn that the EWG uses a lower number than the Environmental Protection Agency set as a limit, CNN reported.