In a large mixing bowl, mix the butter until smooth. Add the peanut butter, and mix well.
Add the vanilla, and slowly add the powdered sugar, mixing well between. The mixture will be crumbly.
Use a medium cookie scoop to scoop out 1 inch balls of the peanut butter mixture.
Roll this mixture into balls.
Freeze the peanut butter balls for 1 hour.
Remove from the freezer, and add the chocolate chips and vegetable oil to a microwave safe bowl.
Heat on 30 second increments, stirring well in between, until melted.
Dip the peanut butter balls into the melted chocolate, and let the excess drip off.
If desired, drizzle any remaining chocolate over some of the balls.
Allow the peanut butter balls to chill for 2 hours, until the chocolate is set.