Preheat the oven to 375 degrees F (190 degrees C).

In a large bowl, cream butter and brown sugar until smooth. Beat in eggs, one at a time, then stir in vanilla. Combine flour, baking soda, and salt in a bowl; stir flour mixture into butter mixture. Mix in oats, chocolate chips, vanilla chips, butterscotch chips, and pecans. Drop tablespoonfuls of dough 2 inches apart onto ungreased cookie sheets.

Bake in batches in the preheated oven for 8 to 10 minutes. Allow cookies to cool on the baking sheets for 5 minutes before removing to a wire rack to cool completely.