In Google Spreadsheet I would like to take only the values from a complete list on one spreadsheet and append it to the bottom of a list on another spreadsheet. My trouble i
As you've found, copyValuesToRange() is a Range method that affects a Sheet Object that is in the same Spreadsheet Object as the Range. There isn't an atomic method that will copy a range of values to another Spreadsheet, but there are a number of ways you could do it.
Here's one way.
getDataRange() and then grabbing all values into a javascript array with getValues().getLastRow().setValues().Script:
function transferList() {
  var sourceSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("RFP List");
  var sourceData = sourceSheet.getDataRange().getValues();
  sourceData.splice(0,1);  // Remove header
  var targetSS = SpreadsheetApp.openById("0ABCD").getSheetByName("RFPData");
  var targetRangeTop = targetSS.getLastRow(); // Get # rows currently in target
  targetSS.getRange(targetRangeTop+1,1,sourceData.length,sourceData[0].length).setValues(sourceData);
}
For some historic dashboard I created by importing and appending data, I use an add-on called Sheetgo. Save me programing time and help me with traceability issues.