In a medium saucepan, combine the sugar, butter, cocoa, and milk. Bring to a slow boil, and simmer until the sugar has dissolved. Stir in the peanut butter and remove from heat. Stir in the coconut and oats. The mixture should be thick.
Line a cookie sheet with parchment paper. Use a cookie scoop to drop heaping spoonfuls on the parchment. Allow the cookies to firm up at room temperature, about an hour.
Excellent make-ahead cookie that can keep for up to a week. Store in an airtight container in the refrigerator.
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