PREHEAT oven to 375°F. Cut chocolate squares in half; cut each half into 3 chunks.

BEAT butter, sugars, egg and vanilla in large bowl with electric mixer on medium speed 1 minute. Add flour, oats and baking soda; beat on low speed until well blended. Stir in chocolate and pecans.

DROP rounded tablespoonfuls of dough, 2 inches apart, onto ungreased baking sheets.

BAKE 10 minutes or until lightly browned. Cool on baking sheets 2 minutes; transfer to wire racks. Cool completely.