Can you transfer a 403b & 401a Retirement Account from one institution to another without paying a tax penalty

Can you transfer a 403b & 401a Retirement Account from one institution to another without paying a tax penalty? I have retired and am considering transferring my 403b & 401a mutual fund accounts to another financial management institution. I've searched the IRS website and can find documents about a rollover from one employer's 401 to another but nothing specifically about transferring post retirement. Any information will be appreciated.