Preheat oven to 300° F. Spray a 9x13 baking dish with nonstick cooking spray. Optionally, line the 9x13 baking dish with parchment long enough that the edges extend for easily lifting the Pecan Chewies from the baking dish for cooling and cutting.
Melt butter in a medium saucepan set over medium heat. Once melted, pour the butter into a large mixing bowl and beat together with granulated, brown sugar, and vanilla extract until well combined. Mix in eggs until well combined, followed by the flour. Stir in the chopped pecans and pour into prepared 9 x 13 baking dish.
Bake until the bars are light brown, about 45 minutes. Allow to cool completely before cutting and serving.