Combine all ingredients in a large bowl; stir well. Pour one-third of mixture into an electric blender; cover and process until smooth, stopping once to scrape down sides. Pour mixture into a 13- x 9-inch pan. Repeat procedure in 2 batches with remaining mixture. Cover and freeze at least 8 hours or until firm.
Remove mixture from freezer, and let stand 10 minutes. Serve immediately, or spoon into an airtight freezer-safe container; cover and freeze for up to 1 month.