Preheat oven to 350 degrees.
If toasting nuts, place them on a baking pan in cold oven.
Remove nuts from oven after 6 minutes. Set aside to cool.
Beat melted butter and both sugars in a large bowl on medium high speed until creamy.
Add eggs, one at a time, beating after each one. Add vanilla, beat until smooth.
Sift flour, baking powder, baking soda and salt together in a small bowl.
Add dry ingredients to butter mixture and stir until a soft dough forms.
Stir in oats, chocolate chips and pecans.
Drop tablespoonfuls of dough 2 inches apart onto greased (or parchment-covered) baking sheets. (A scoop makes this easier.)
Bake 10-12 minutes, or until lightly browned around the edges.
Remove from oven but leave cookies on baking sheet for two minutes before removing to cool on a wire rack. The heat will finish cooking the cookies.
Store in an airtight container for up to a week.