Ottawa - MTL is almost entirely on a paved shoulders and part is on the rather busy highway 148. The Ontario side is quieter.
Le P'tit Train du Nord is all path, and it extend south towards MTL. You can take a transport from MTL or St-Jérôme that will carry you and your bike and gear to Mont-Laurier. The southern half is crushed stone but very rideable.
You can link trails from MTL to Quebec City via Granby. This is mostly on crushed stone. Easy riding but a bit boring in parts.
Another good trail is the "Cheminots" path and
Jacques-Cartier trail from Quebec City to Rivière-à-Pierre. It's about 100km from the City center to the northwest end.
Le
Petit Témis looks interesting but I've never cycled it myself.
The
Véloroute des Bleuets would be an excellent choice. About 256km around Lac St-Jean on paved, crushed stone and quiet streets with a good mix of culture and nature.