Heat oven to 350 degrees F. Have two large nonstick baking sheets ready.
Combine flour, cocoa powder, baking soda, and salt in a bowl; set aside.
In bowl of electric mixer, beat butter and both sugars until creamy, about 3 minutes.
Beat in eggs and vanilla. On low speed, beat in flour mixture, then stir in oats, raisins, and chocolate chips.
Dollop ¼-cupfuls of batter onto baking sheets. Bake cookies for 17 minutes. (Note: I thought that was too long. I baked them for 12-13 minutes and they were perfect).
Remove from oven and let cookies cool on the baking sheet for 4 to 5 minutes, then transfer to wire racks to cool. Makes about 16 to 20 cookies.
Recipe by The Culinary Cellar at https://theculinarycellar.com/cocoa-oatmeal-jumbos/