Holding just a 1-0 advantage from the first leg, Pep Guardiola named a reasonably strong side for the match against Segunda Division B opposition.
Pedro kicked off the scoring with a 12th-minute penalty before goals from Andres Iniesta (19), Thiago Alcantara (23), Xavi (36) and Cristian Tello (43) made it 5-0 at the interval.
Isaac Cuenca scored twice in the second half, Tello also notched a second and Thiago slotted a 55th-minute penalty.
Valencia were 4-0 winners at home to Cadiz after a 0-0 draw in the first leg.
Victor Ruiz scored after five minutes, Jonas followed up in the 27th minute, while Roberto Soldado (41) and Ever Banega (68) were also on target.
On Wednesday, Villarreal went down 2-0 at El Madrigal against the third-tier Mirandes outfit in the second leg of their fourth-round tie to crash out of the cup 3-1 on aggregate.
Pablo Infante scored both of Mirandes' goals, while Villarreal had Mateo Musacchio sent off late on.
Atletico Madrid were knocked out by Segunda Division opposition in the form of Albacete.
Victor Curto scored the only goal in the first minute to seal a 1-0 win and 3-1 aggregate success.
Other shock exits saw Alcoron see off Real Zaragoza and Real Betis go out despite victory over Cordoba.
Alcoron won 2-0, with Oriol Riera and Joaquin Quini both notching in the last three minutes, for a 3-1 aggregate win.
Cordoba lost 2-1 at Betis as Jorge Molina's brace bettered Garcia Borja's effort, but the lower-ranked side progressed on away goals. Cerra saw red for Cordoba two minutes from time.
Away goals also came into play as Rayo Vallecano beat Racing Santander 4-3 at home, only to see their opponents go through after the tie ended 6-6 over the two games.
Two from Christian Stuani and one from Alexis Tziolis provided Racing with the vital three goals, while Medina Piti, Miguel Michu, Andrija Delibasic and Raul Tamudo were on target for Rayo.
Levante won their clash against Deportivo La Coruna in extra-time with an eventual 4-1 win on the night.
Nabil El Zhar, Sergio Ballesteros and Ruben Suarez all scored in normal time for Levante, while Depor's Pablo Alvarez also netted.
That left the scores matched after 180 minutes, leaving Arouna Kone to seal it 11 minutes into the first period of extra-time.
Borja was sent off for a second yellow in the dying seconds.
Another eye-catching fixture, between Malaga and Getafe was decided when Diego Buonanotte put the former through five minutes after coming on as an 80th-minute substitute.
The score on the night was 2-2 - Willy Cabellero's own-goal and Mane's effort going in after Ruud van Nistelrooy's strike - handing Malaga the tie following their earlier 1-0 win.
Malaga had also coped with Weligton's sending off in the 77th minute.
A 1-1 draw was enough to see Osasuna through 4-2 overall, at the expense of Almeria.
Roland Lamah and Henok Goitom were on target as the game came to life in the last 10 minutes.
Athletic Bilbao repeated their first-leg 1-0 win over Real Oviedo, with Ander Herrera the scorer on Wednesday night.
A 2-1 win for Granada over Real Sociedad was not enough to prevent a 5-2 defeat in the tie.
Guilherme Siqueira's penalty and Alexandre Geijo's follow-up came before Imanol Agirretxe's riposte but, with the visitors' three-goal cushion, it was largely academic.
Tuesday's action saw Real Madrid put five goals past Ponferradina to go through 7-1 on aggregate, while Sevilla overcame San Roque 2-1 on the night to progress to the next round.
Real Mallorca overcame a one-goal first-leg deficit by defeating Sporting Gijon 2-0, while Espanyol beat Celta Vigo 4-2 after a goalless first leg.
Thursday's Copa del Rey Results
Barcelona 9-0 L'Hospitalet (10-0 on aggregate)
Valencia 4-0 Cadiz (4-0 on aggregate)
Wednesday's Copa del Rey Results
Atletico Madrid 0-1 Albacate (1-3 on aggregate)
Villarreal 0-2 Mirandes (1-3 on aggregate)
Osasuna 1-1 Almeria (4-1 on aggregate)
Real Zaragoza 0-2 Alcorcon (0-2 on aggregate)
Real Betis 2-1 Cordoba (2-2 on aggregate, Cordoba on away goals)
Levante 4-1 Deportivo La Coruna (5-4 on aggregate, after extra time)
Rayo Vallecano 4-3 Racing Santander (6-6 on aggregate, Racing on away goals)
Malaga 2-2 Getafe (3-2 on aggregate)
Granada 2-1 Real Sociedad (3-5 on aggregate)
Athletic Bilbao 1-0 Real Oviedo (2-0 on aggregate)
Tuesday's Copa del Rey Results
Real Madrid 5-1 Ponferradina (7-1 on aggregate)
Espanyol 4-2 Celta Vigo (4-2 on aggregate)
Sporting Gijon 0-2 Real Mallorca (1-2 on aggregate)
Sevilla 2-1 San Roque (3-1 on aggregate)