Preheat oven to 350°F (175°C).

In a large bowl, beat softened butter and both brown and granulated sugars together with an electric mixer until creamy.

Add eggs and vanilla extract to the butter mixture and beat until well combined.

In a separate bowl, lightly spoon flour into dry measuring cups and level with a knife.

Combine flour, baking soda, and salt in the bowl and stir well to combine.

Add uncooked rolled oats to the dry ingredients and stir well.

Gradually add the dry ingredients to the butter mixture and stir until well blended.

Gently stir in the semisweet chocolate chunks and chopped toasted pecans.

Drop by rounded tablespoons, about 2 inches apart, onto baking sheets lined with parchment paper.

Bake in the preheated oven for 10-12 minutes, or until the edges are golden brown but the center still looks a bit gooey.

Let the cookies cool on the baking sheets for 2 to 3 minutes, or until firm enough to handle.

Transfer the cookies to wire racks to cool completely.