In a medium bowl, mix together 1 cup sugar and vegetable oil. Stir in the egg and vanilla until smooth. Combine the flour, baking powder and salt; gradually stir into the sugar mixture. Mix in mint chocolate chips. Roll the dough into walnut sized balls. Roll each ball in the remaining 1/4 cup of sugar to coat. Place the cookies 2 inches apart onto the cookie sheet.
Bake for 8 to 10 minutes in the preheated oven. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.
