Both players missed out on selection for the World Cup but their early season form has seen new La Roja manager Luis Enrique bring them back in from the cold.
Morata has led the line for the Blues in each of their three Premier League matches to date, ending a long goalscoring drought with a strike in victory over Arsenal.
Alonso, meanwhile, netted the winner against the Gunners before playing a major role in both goals in the win over Newcastle at St James' Park.
Alonso's inclusion means there is no place for Barcelona full-back Jordi Alba nor Arsenal's Nacho Monreal - both of whom were selected by Julen Lopetegui for the World Cup.
Alba's absence is particularly eye-catching given Luis Enrique left him out of his Barca side with regularity during his time in charge at Camp Nou - something Alba has critcised him for since returning to the starting 11 under Ernesto Valverde.
There is a recall for Alba's club-mate Sergi Roberto, though the midfielder is one of just two Blaugrana representatives in the squad alongside Sergio Busquets.
Real Madrid midfielder Dani Ceballos is one of the other new faces, joining his Blancos team-mates Sergio Ramos, Nacho, Isco and Marco Asensio, but there is no place for Atletico Madrid midfielder Koke.
AC Milan forward Suso also earns a place in the squad following some fine performances for the Rossoneri over the past two seasons.
Spain are looking to get back to winning ways having failed to go further than the last 16 in any of their last three major tournament appearances, most recently losing to hosts Russia on penalties at the World Cup.
That brought the curtain down on the international careers of World Cup-winners Andres Iniesta and Gerard Pique, with Luis Enrique tasked with promoting a lot of the country's talented youngsters into the senior ranks.
Full Spain squad
Goalkeepers: De Gea, Kepa, Pau Lopez
Defenders: Carvajal, Azpilicueta, Albiol, Nacho, Ramos, D Llorente, Inigo Martinez, Gaya, M Alonso
Midfielders: Busquets, Sergi Roberto, Rodri, Saul, Thiago, Ceballos, Isco
Forwards: Asensio, Morata, Costa, Suso, Rodrigo