A date for the opening debate - and a crunch vote on the timetable for its progress - will be announced by Commons Leader Sir George Young. It will be held before MPs depart for their summer recess on July 17.
"We have been discussing this issue for 100 years and it really is time to make progress," Mr Cameron said.
"There are opponents of Lords reform in every party. But there is a majority in this House for a mainly-elected House of Lords and I believe there's a majority for that in the country. If those who support Lords reform don't get out there and back it, it won't happen. That is the crucial point."
He attacked Labour leader Ed Miliband as "hopeless" for backing the reforms but seeking more days to be allocated to debating the legislation. Labour is to join with Conservative rebels to vote down a motion setting out its passage through parliament.
The Bill, approved by Cabinet with "strong support" from ministers, is being driven by Deputy Prime Minister Nick Clegg as the remaining centrepiece of Liberal Democrat constitutional reform plans, following defeat in last year's referendum on voting reform.