The two Balkan nations have made enough progress to join the bloc on Jan. 1, 2007, the commission said in a much-anticipated report recommending that the 25 EU governments accept them.
But it added that a significant chunk of expected economic aid should be made conditional on the completion of further reforms needed in justice and home affairs, as well as food safety and state subsidies.
The decision to admit two of the poorest nations in Europe comes at a time of growing doubts about whether the bloc's rapid expansion should continue to take in nations such as Turkey and Croatia in coming years.
EU leaders will meet next month to give formal approval to Romania and Bulgaria whose bid for membership bid had been stalled due to their spotty records on fighting corruption.
"Bulgaria and Romania have made further progress to complete their preparations for membership, demonstrating their capacity to apply EU principles and legislation from Jan. 1, 2007," said the report presented by European Commission President Jose Manuel Barroso and the EU's expansion commissioner, Olli Rehn.
Barroso said the entry of the two nations into the bloc would be a "historic achievement."
Both countries will face restrictions in terms of their work force gaining access to other European Union markets. Britain, Sweden and Ireland, which opened the door to workers from the 10 newcomers who joined in 2004, are likely to set the strictest conditions. But they may also be shut out of labor markets in Hungary, Slovakia and the Czech Republic -- themselves battling restrictions by countries further west.
Bulgaria and Romania will have to regularly report on progress of their reform to Brussels, with the first report to come on March 31, 2007.