The programme will end in December, but the ECB's policy stance will remain extremely accommodative in 2019.
Despite a slight downward revision to its inflation forecast, the bank is preparing to end monthly asset purchases.
The legislation seeks to expand the ambit of regulation for financial products such as bonds, stocks and derivatives.
An announcement on tapering will be made in October, but the ECB will remain wary of reducing QE too fast and too soon.
Currency markets ignored the ECB's cautious tone, interpreting plans for a discussion on QE as a step towards tapering.