The epic Battle of Endor featured the entire Rebel fleet of capital ships. Six or more Mon Calamari cruisers (two were lost, and four more can be seen when Executor goes down), a few Nebulon-B frigates, even more CR90 Corvettes and GR-75 Medium Transports.
However, what puzzles me is: why were they brought there? The whole plan was for the fighter group to fly into the superstructure and blow up the reactor.
So, what was the role of the capital ships? Since the goal is to blow up the reactor anyway, bombarding the station serves little purpose, especially since it might have had operational turbolasers, presenting a threat to the ships.
Ackbar mentions that:
(...) our cruisers will create a perimeter while the fighters (...)
What does that entail? Surely, not engaging the supposedly absent Imperial Fleet. Intercepting potential evacuees? Because, a wing of A-Wings would perform infinitely better than an MC80 cruiser.