HEAT oven to 375°F.
COMBINE flour, oats and baking soda; set aside. Beat butter and sugars in large bowl with mixer until light and fluffy. Blend in egg and vanilla. Gradually add flour mixture, beating well after each addition. Stir in chocolate and nuts.
DROP rounded tablespoonfuls of dough, 2 inches apart, onto baking sheets.
BAKE 10 min. or until lightly browned. Cool on baking sheets 2 min. Remove to wire racks; cool completely.