Heat the oven to 350°F.
Melt the chocolate in a small saucepan over very low heat, stirring to prevent any scorching, and then set it aside to cool.
In a large bowl, cream together the butter and sugar with an electric mixture on medium speed until the mixture looks pale yellow and fluffy.
After the melted chocolate has cooled sufficiently that it is no longer hot to the touch, add it to the butter and sugar mixture along with the vanilla extract and the egg. Beat everything together on medium speed until mixture looks fluffy again.
In a separate medium bowl, whisk together the flour, baking soda, and salt.
Add the flour mixture to the chocolate mixture and stir just long enough to combine everything into a sticky dough.
Mix in the chopped pecans and rolled oats until they are evenly distributed.
Divide the cookie dough into small pieces and roll into balls. Place the balls about two inches apart on an uncreased baking sheet.
Bake for 10 to 12 minutes or until the edges of the cookies are firm.