The Canada-EU Summit will discuss shared concerns like the conflicts in Ukraine, Syria and Iraq. But the main event will be a photo opportunity to mark the successful conclusion of negotiations toward a Comprehensive Economic Trade Agreement (CETA.)
The final text of the agreement was posted on the Canadian government's website on Friday morning.
Talks concluded over the summer, but the final agreement was not made public because officials said it needed to be translated and checked by lawyers.
Barroso's presidency ends within days. This trade agreement is the EU's second under his leadership. (The first, with South Korea in 2011, is still being ratified in parliaments across Europe.)
Harper and Barroso announced the end of negotiations in August.
The European Council and the European Parliament must now approve the deal.
Despite earlier indications that it wouldn't be necessary, individual European countries' parliaments now seem poised to vote on ratification as well.
Opponents say there is significant opposition in Germany as well as France, Italy, Austria, Belgium and Luxembourg. A tight vote is expected at the European Parliament.
In Canada, the agreement will be voted on in the House of Commons and Quebec's National Assembly, with other provincial cabinets also signing off. It's expected to pass with broad support.
After a working lunch in Ottawa, the leaders will head to Toronto to promote the trade deal at an event with business leaders from Canadian and European companies.