The word desayunaron is the preterite form of desayunar in the third person plural.
See the full desayunar conjugation

desayunar

Los hombres desayunaron y volvieron a trabajar.
The men had breakfast and went back to work.
Al parecer miraron una película y desayunaron temprano.
It looks like they watched a movie, had an early breakfast.
Los hombres se levantaron temprano, desayunaron y se pusieron sus trajes espaciales.
The men rose early, ate breakfast, and dressed in their space suits.
¿Los chicos desayunaron bien?
Did the children have a good breakfast?
¿Qué desayunaron el sábado?
What did they have for Saturday breakfast?
Díganme, ¿qué desayunaron hoy?
So, what did you have for breakfast?
Los eventos insignificantes, tales como qué desayunaron, no serán archivados en el largo plazo o en la memoria del alma.
Insignificant events, such as what you had for breakfast, will not be filed in the long-term or the soul memory.
Y cuando el sol asomó por la ventana y Nuestro Señor se hubo levantado, desayunaron los tres juntos, y Nuestro Señor se dispuso a seguir su camino.
When the sun shone in through the little window, and the Lord had got up, he again ate with them, and then prepared to set out on his journey.
Hagan un dibujo de lo que desayunaron.
Draw a picture of what you ate for breakfast.
¿Qué desayunaron? - Comimos panqueques.
What did you have for breakfast? - We ate pancakes.
Me dijo su madre que ustedes primero desayunaron y que, luego, hicieron las maletas y se fueron al aeropuerto.
Your mother told me that you first had breakfast, and that you then packed your bags and left for the airport.
El 11 de septiembre, un martes cualquiera de una semana cualquiera, los salvadoreños desayunaron viendo las imágenes de destrucción que en vivo y directo transmitía la televisión nacional.
The morning of September 11, what should have been an average Tuesday in an average week, many Salvadorans flipped on the TV as they ate breakfast.
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