Marbled chocolate chip oatmeal cookies

In large bowl, beat butter and sugars until creamy. Add eggs and vanilla; beat well. Add combined 4 cups flour, baking soda and salt; mix well. Divide dough evenly between two bowls. Add cocoa to one bowl and add remaining 1/4 cup flour to second bowl; mix well. Add 1 cup chocolate chips and 1 cup oats to each bowl; mix well. Cover and chill both doughs 2 hours. Heat oven to 375°F. To shape cookies, remove small portion of each dough; keep remainder refrigerated. Combine 1 tablespoon of each dough, twisting doughs together to form a single cookie. Place 2 inches apart on ungreased cookie sheets. Bake 10 to 11 minutes or until light coloured dough is golden brown. Cool 2 minutes on cookie sheets; remove to wire rack. Cool completely. Store tightly covered.