Beat butter at medium speed with an electric mixer until creamy; gradually add sugar, beating well. Add eggs, 1 at a time, beating just until blended.
Add cocoa and vanilla; beat at low speed 1 minute or until blended. Gradually add flour, beating well.
Stir in pecans and chocolate morsels. Pour batter into a greased 13- x 9-inch baking pan.
Bake at 350° for 30 to 35 minutes. Cool and cut brownies into squares.