This study examines child L2 English experimental production to address whether language mode (i.e., oral versus written) helps shape the interplay between explicit instruction and length of exposure and the role they have in L2 attainment. English noun-noun compounds (NNs) are targeted given the different productivity and word-order configuration they exhibit when comparing English (the participants’ L2) and Spanish (their L1): while NNs are right-headed and productive in English, they are left-headed and non-productive in Spanish with other alternative structures being used instead. Despite these differences, English NNs hardly ever make it to the L2 English classroom in the Spanish context. Four L1 Spanish-L2 English participant groups have been considered: two involved in an explicit NN instruction program (9-year-old and 11-year-old group); and two age-matched groups following regular non-NN instruction. Children have been tested via an oral free production task (a director-matcher task simulating a board game) and a written guided production task (a picture naming task). Results show that explicit instruction has a positive effect since both production and correctness rates are higher in the instruction group; that length of exposure also has a parallel effect that is accentuated when combined with explicit instruction; and that language mode helps tune the role played by the instruction variable which remains stable regardless of whether production is oral or written. This has a double implication: that explicit teaching of grammatical properties is effective and that the productivity of English NNs is something that can actually be taught.