In the bowl of an electric mixer fitted with the paddle attachment, beat pumpkin puree, peanut butter and milk on medium-high until well combined, about 1-2 minutes. Gradually add 2 1/2 cups old fashioned oats at low speed, beating just until incorporated.

Using a small cookie scoop, roll the mixture into 1 1/4-to-1 1/2-inch balls, forming about 20. Dredge balls in remaining 1/2 cup old fashioned oats, pressing to coat.

Cover and place in the refrigerator until firm, about 1 hour.*