SQL Server Setup Control /QS: Optional Specifies that Setup runs and shows progress through the UI, but does not accept any input or show any error messages.

/QS is Upper case

You should use Upper case for all parameters since they are all Upper cases: Install SQL Server 2014 from the Command Prompt

Setup.exe /QS /ACTION=Install /FEATURES=IS /INSTANCENAME=MSSQLServer /IACCEPTSQLSERVERLICENSETERMS 

SQL Server Setup Control /QS: Optional Specifies that Setup runs and shows progress through the UI, but does not accept any input or show any error messages.

/QS is Upper case

You should use Upper case for all parameters since they are all Upper cases: Install SQL Server 2014 from the Command Prompt

/QS Specifies that Setup runs and shows progress through the UI, but does not accept any input or show any error messages.

I think you should use /Q + /INDICATEPROGRESS:

Setup.exe /Q /ACTION=Install /FEATURES=IS /INSTANCENAME=MSSQLServer /IACCEPTSQLSERVERLICENSETERMS /INDICATEPROGRESS

All the output will be shown on the command line.