How to wait all batch files to finish before exiting?

I think this is the simplest and most efficient way:

@echo offecho %time%(    start call batch1.bat    start call batch2.bat    start call batch3.bat    start call batch4.bat) | set /P "="echo %time%

In this method the waiting state in the main file is event driven, so it does not consume any CPU time!

EDIT: Some explanations added

The set /P command would terminate when anyone of the commands in the ( block ) outputs a line, but start commands don't show any line in this cmd.exe. This way, set /P keeps waiting for input until all processes started by start commands ends. At that point the pipe line associated to the ( block ) is closed, so the set /P Stdin is closed and set /P command is terminated by the OS.

give a unique title string to the new processes, then check if any processes with this string in the title are running:

start "+++batch+++" batch1.batstart "+++batch+++" batch2.batstart "+++batch+++" batch3.batstart "+++batch+++" batch4.bat:loop  timeout /t 1 >nul  tasklist /fi "windowtitle eq +++batch+++*" |find "cmd.exe" >nul && goto :loopecho all tasks finished

(find is used, because tasklist does not return a helpful errorlevel)

Give this a try.

@echo offecho %time%start "" /wait cmd /c bat1.bat |start "" /wait cmd /c bat2.bat |start "" /wait cmd /c bat3.batecho %time%pause