This contribution presents the preliminary findings from the TEPS study ("Teaching English in Primary Schools"). The study is situated in Germany where primary foreign language (FL) education has been compulsory since 2004, with pupils beginning FL education -- mostly English as a FL (EFL) -- in either year 1 or 3. Generally, this introduction of primary FL education has not been empirically evaluated, in spite of various open research questions: (1) Does the receptive EFL proficiency of learners at the end of primary education in year 4 differ depending on their learning time (duration & age of onset)? (2) Is there a correlation between teaching quality (learners' perspective) and learners' receptive EFL proficiency as well as their attitudes towards learning EFL? Prior studies (e.g. Demircioglu, 2010) gave first indications that learners with an earlier start achieve better receptive skills. Yet, findings from these samples cannot be generalized and are altogether inconclusive (e.g. Jaekel, van Ackern, Schurig, & Ritter, 2017). Studies investigating correlations between teaching quality and learner achievements in primary school are mainly based in maths and science education (e.g. TIMSS-2015: see Rieser, Stahns, Walzebug, & Wendt, 2016). Thus, the TEPS study situated in both applied linguistics and educational science is addressing some of these research deficits by (a) testing pupils' receptive EFL proficiency at the end of primary education in year 4 (n= 269) and (b) surveying teaching quality and learner attitudes towards EFL. The study has been conducted in two federal states with different ages of onset (year 1 vs. year 3). Aside from the theoretical background and context of the study this paper will present the complex research design followed by preliminary findings from the pilot study giving insights into the questions raised above (for the main study see Wilden, Porsch, & Schurig, 2020).