MARS, which had already lifted its 2015 corn yield estimate last month after cutting it several times due to hot and dry weather in the bloc, put grain corn yields at 6.47 tons per hectare (t/ha), up from 6.43 t/ha estimated last month.
That was 20.7 percent below a revised estimate of 8.07 t/ha last year and down 8.0 percent on the five-year average.
MARS in its monthly report also raised its estimate for this year's soft wheat yield to 5.86 t/ha against 5.81 t/ha estimated in September, now down 4.6 percent on 2014 but 3.4 percent above the five-year average.
It increased its barley yield estimates, including winter and spring varieties, to 4.65 t/ha from 4.63 t/ha in September and down 5.1 percent on last year.
In oilseeds, it left unchanged its estimate for the EU's 2015 rapeseed yield at 3.25 t/ha, down 10.3 percent on last year.
MARS, which gave no reason for its yield revisions, lowered its forecast for this year's sugarbeet yield in the bloc to 70.48 t/ha, from 70.54 t/ha seen last month and 8.4 percent below a revised estimate for 2014.
For the 2016 harvest, MARS stressed adverse weather had affected winter grain sowings in the eastern and northern parts of the bloc but said they had progressed without major problems in the EU's top producing countries France, Germany and the UK.
The monitoring service did not give yield estimates for next season but noted that dry weather had persisted in Poland, Lithuania, western Ukraine and southern Russia, which could hurt winter crops.
"In these regions, the winter crops sown in September germinated under unfavourable conditions which further worsened due to the low temperatures that occurred in October," MARS said.
It noted that large areas in southeastern Europe had faced a period of abundant rains, which hampered winter crop sowings.