Preheat oven to 350 degrees F. Line two baking sheets with parchment paper; set aside.
In a large bowl, whisk together the oats, flour, malted milk powder, baking powder, baking soda and salt; set aside.
With an electric mixer, cream together the butter and sugars on medium speed until light and fluffy, 3 to 4 minutes. Add the eggs one at a time, beating well and scraping the bowl after each addition. Reduce the mixer speed to medium-low and slowly add the milk, and then the vanilla extract. Mix until well combined. Reduce the mixer speed to low and gradually add the oat mixture, mixing until barely combined. Using a rubber spatula, mix in the chocolate chips, chopped peanuts and pretzels.
Using a large cookie scoop, drop mounds of dough on the cookie sheet, about 2 inches apart. Bake for about 12 minutes, or until they are just set and light brown around the outside, but still pale and puffy in the middle. Cool on the baking sheet for 5 minutes, and then transfer to a wire cooling rack to cool completely. Store cookies in an airtight container at room temperature.