If you enjoy a salted glass, prep the rim of your glass by rubbing a lime wedge along the rim. Dip in tequila salt, and set aside.
Blend:
Add the tequila, Cointreau or triple sec, lime juice, simple syrup, blueberries, and the ice to your blender jar. Blend until you have a smooth slushy consistency.
Serve:
Pour the frozen blueberry margarita into the prepared glasses. Garnish with a lime wedge.