The following table contains a list of cereal grains and flours and their antioxidant content. Cereals are rich in diverse kinds of antioxidants. Generally, the bran and germ parts of the grain are where most of the antioxidants are contained.

Total antioxidant activity in cereals:

 

Cereals	Antioxidant Content (FRAP mmol/100 g FW)
Buck wheat, wholemeal flour	1.99
Buck wheat, white flour	1.23
Barley, wholemeal flour	1.09
Common millet, wholemeal flour	0.82
Maize, white flour	0.60
Oats, rough oatmeal	0.59
Barley, white flour	0.58
Rye, wholemeal flour	0.47
Wheat, wholemeal flour	0.33
Oats, white flour	0.32
Bulgur wheat, wholemeal flour	0.31
Sorghum, wholemeal flour	0.30
Common millet, white flour	0.25
Rye, white flour	0.23
Rice, grains	0.17
Wheat, white flour	0.13
Durum wheat, white flour	0.05
Rice, white flour	0.04

Antioxidant content was determined by the FRAP assay. Values represent mean concentration per 100 g fresh weight of edible portion if not otherwise stated. Cereal samples were obtained from various countries and the antioxidant content is a mean of cereals from at least three locations or brands.

 

More lists of food sources high in antioxidants :
Fruits, vegetables, nuts
Vegetables
Fruits -I
Fruits - II
Black and green tea, wine, coffee
Whole grain breakfast cereals
Dark chocolate and other cocoa products

Reference:
Bente L. Halvorsen, Kari Holte, Mari C. W. Myhrstad, Ingrid Barikmo, Erlend Hvattum, Siv Fagertun Remberg, Anne-Brit Wold, Karin Haffner, Halvard Baugerød, Lene Frost Andersen, Ø. Moskaug, David R. Jacobs, Jr. and Rune Blomhoff. 2002. A Systematic Screening of Total Antioxidants in Dietary Plants. J. Nutr. 132:461-471.