The scientific potential of European countries measured by their participation in publication of all peer-review journals as well as open access journals (OAJs) is significant. In this paper we focus on European fully open access journals (OAJs) as a potentially optimal channel of communication in science. We explore fully OAJs (n=1201) indexed by Scopus with several bibliometric indicators: quartile rankings, SJR (SCImago Journal Ranking) and h-index. As countries in our focus have entered EU at different times and have diverse backgrounds, we divide them into three groups: A (members before 1995), B (became members in 2004-2013 period) and C (EU candidate countries). Analysis across country groups is complemented with analysis across major subject fields. Quartile rankings indicate that journals in Q1 dominate in group A, followed by journals in Q2. In the remaining two country groups, journals belonging to Q3 have more than 50% of the share. Analysis by different scientific fields stresses that life and health sciences have the highest shares of OAJs in Q1. In physical sciences the highest share of OAJs is in Q3 while combined shares of Q2 and Q3 are above 50%. Only 10% of all European OAJs in social sciences is in Q1. Furthermore, we find the least difference between journals in group A and groups B and C in social sciences, both in respect to coverage and quality indicators. In all scientific fields median SJR indicators is, in the case of groups B and C, higher for OAJs than non-OAJs as opposed to group A.