12 slices fresh cucumber (about 1/3 of a medium cucumber)
1/2 cup fresh lime juice
4 ounces (1/2 cup) Cointreau or triple sec
6 ounces (3/4 cup) tequila reposado
6 cups ice
1/4 cup Grand Marnier or triple sec
Combine cucumber and next 4 ingredients in a blender; process until smooth.
Pour into glasses. Top each serving with a tablespoon of Grand Marnier, and garnish with lime.
--Adapted from Cooking Light magazine