There aren’t that many major events that occur in this region of Croatia. However, there are still plently of small, local ones such as concerts or food and wine events! To find out about these, the best idea would be to look up the Events sections on websites such as:

Baranja info: http://www.tzbaranje.hr/en

Đakovo info: http://www.tz-djakovo.hr/index.php?j&j=1

Kutjevo info: http://www.tz-kutjevo.hr

Lipik info: http://www.lipik.hr

Našice info: http://www.tznasice.hr

Orahovica info:  http://www.tzgorahovica.hr

Osijek info: http://www.tzosijek.hr/index.php/en/city-guide-2/cultural-events

Požega info: http://www.pozega-tz.hr

Vinkovci info: http://www.tz-vinkovci.hr/hr

Virovitica info: http://www.tz-virovitica.hr/en

Vukovar info: http://www.turizamvukovar.hr

or, alternatively, check locally when visiting the area.