Dark Chocolate Oatmeal Cookies

• 3/4 cup all purpose flour
• 1/4 cup unsweetened cocoa powder
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt
• 1/2 cup (1 stick) unsalted butter, room temperature
• 1/2 cup sugar
• 1/2 teaspoon vanilla extract
• 2 tablespoons steel-cut oats
• 1/4 cup semisweet chocolate chips