The role of first language (L1) skills in second language (L2) achievement is often investigated to assist learners in acquiring their L2. There are several factors that may influence potential relations among Spanish and English measures (e.g., age of L2 acquisition, social status, among others). This study investigates relations among L1 and L2 variables for language learners. Specifically, it focuses on relations among oral language (vocabulary), reading (word reading and reading comprehension) variables and sociocultural variables (language dominance, acculturation, socio-economic status) in Spanish-English bilinguals, all of whom were attending school in a large metropolitan, English-speaking region in Canada. Results showed that in both English and Spanish, reading and oral language variables were related. Reading comprehension was related to word reading and vocabulary in the given language. Additionally, reading comprehension in Spanish was related to dominance in that language and to affiliation with the heritage culture.