In a large bowl, cream the butter, brown sugar and white sugar until smooth.
Add the eggs one at a time, beating after each addition. Stir in the milk and vanilla. Sift together the flour, baking powder, baking soda and salt, stir into the creamed mixture. Using a wooden spoon, stir in the rolled oats, chocolate chips and walnuts.
Roll the dough into walnut sized balls, and place 2 inches apart on an unprepared cookie sheet.
Bake for 10 to 12 minutes in the preheated oven. Cool cookies on wire racks.