It depends a little on what mail client you use. I've not used Outlook for about 15 years: the latest version may be more competent than the last one I used.
"Reply All" won't include the bcc addressees since their addresses aren't included in the copy you received. Your mail client won't know who they are.
Reply All should include the originator and any To: and Cc: addressees in the original.
I use Thunderbird: all the "sent mail" copies include the full list of bcc addressees so I know who I've sent to.