Melt butter in a saucepan over medium heat. Stir in sugar, milk, and cocoa powder. Bring to a boil, stirring constantly, and let it boil for exactly 1 minute to ensure the cookies set properly.
Remove the saucepan from heat and quickly mix in the peanut butter, vanilla extract, and salt. Stir well until the peanut butter is completely melted into the mixture.
Add the quick oats and stir until fully coated. The mixture should be thick and well combined. For another delicious chocolate dessert, check out Fudgy Brownie Cookies!
Drop spoonfuls of the mixture onto a parchment-lined baking sheet. Flatten slightly if desired, then let them sit at room temperature.
Allow the cookies to cool and firm up for about 20–30 minutes. Once set, enjoy your homemade No Bake Cookies with a cold glass of milk!