The home side had the better of the chances in the first period, but trailed at the interval to a goal from Oscar Gonzalez.
The home side were not finished, however, as Gomez scored his second late on, before Ander Herrera added a fourth.
Valdet Rama registered a late consolation for Valladolid, but it was a case of too little too late for the visitors as Bilbao continued their unbeaten home record this season.
Read how it all unfolded in Sports Mole's minute-by-minute live commentary of the action below.
BILBAO: Iraizoz; Iraola, Gurpegi, Laporte, Balenziaga; Iturraspe, Benat; Susaeta, Herrera, Ibai; Aduriz
VALLADOLID: Marino; Rukavina, Valiente, Pena, Bergdich; Rubio, Perez, Rossi, Ebert; Oscar, Guerra