2 cups all purpose flour

2 cups old-fashioned oats

1 teaspoon baking soda

1/2 teaspoon baking powder

1/2 teaspoon salt

1 cup (2 sticks) unsalted butter, room temperature

3/4 cup sugar

3/4 cup plus 2 tablespoons packed dark brown sugar

2 large eggs

1 teaspoon vanilla extract

1 1/2 cups semisweet chocolate chips

1 cup chopped toasted walnuts (about 4 ounces)

Whisk first 5 ingredients in medium bowl to blend, then set aside. Using an electric mixer, beat the butter and both sugars in a large bowl until light and fluffy. Add eggs and vanilla. Mix thoroughly. Add dry ingredients and beat until just blended. Stir in chocolate chips and walnuts. Cover dough and chill 1 hour. Preheat oven to 350 F. Form dough into balls, using 1/4 cup dough for each. Place on greased baking sheets, spacing 2 inches apart. Flatten with hand to 3-1/2-inch rounds. Bake 10-15 minutes or until cookies are golden brown around edges and firm in center. Transfer to cooling racks to cool completely.