Using a large cutting board, cut the limes and lemons in half. Squeeze juice into a large glass measuring cup, removing any seeds with a fine mesh strainer. Pour into a large glass pitcher.
Do the same for oranges, or use orange juice that is already made.
Once the juices have been added, stir in the agave syrup, and Cointreau. Finish with desired amount of Tequila. Start with 1 cup and taste, then add more if desired. Stir well.
Line margarita glasses or jars with lime juice and dip in sea salt. Fill glasses with small cubed ice. Pour tequila mixture over ice and serve. Serves 4-6.
Notes
*To make a Frozen Margarita, add all ingredients to a blender and mix along with 12-14 ice cubes until ice has been crushed. Pour into prepared glasses. Serve immediately.