No one food meets the Daily Reference Intake (DRI) for Folate or Folic Acid (1.3-1.7 mg) in a single serving. You need to eat several Folic Acid rich foods each day. Most Americans DO NOT consume the DRI for Folic Acid, but supplementation in high doses (over 200mg) can cause nerve damage.
Italicized foods have 50% of the DRI (400 micrograms) per usual serving.
The foods below are listed from highest to lowest folate content.