The association slightly raised its harvest forecasts for both crops after rain in much of Germany.
Germany's 2017 wheat crop will increase 3 percent on the year to 25.20 million tonnes, the association estimated.
The country's 2017 winter rapeseed crop will increase 4.7 percent on the year to 4.78 million tonnes, it said.
In its last estimate in May, the association had forecast a German 2017 wheat crop of 24.98 million tonnes and a rapeseed crop of 4.68 million tonnes.
"Overall, grain crops are in a good to satisfactory condition," the association said in a harvest report. "Rainfall in the past weeks was in sufficient volumes apart from a few regions in western Germany."
"This contributed to preventing yield loss, especially in wheat."
There had been concern about stress to crops after a very dry start to the spring.
Germany is the European Union's second largest wheat producer after France and in most years the EU's largest producer of rapeseed, Europe's main oilseed for edible oil and biodiesel production.
Barley is ripening rapidly, the association said. In early harvesting areas in southern Germany farmers will start gathering their crops in June, in line with the long-term time schedule.
Germany's crop of winter barley, largely used for animal feed, is set to fall 2.3 percent on the year to 8.74 million tonnes, the association said.
The spring barley crop, used for beer and malt production, will rise 7.4 percent to 1.90 million tonnes.
The grain maize (corn) crop will fall 5.7 percent to 3.78 million tonnes.
The rain which had benefited other crops had hindered spring maize sowings and the total maize area sown will be reduced by 5.7 percent to 392,000 hectares, it said.