This study examines the role Language Dominance plays in determining the source of transfer in the Initial Stages of L3 processing by investigating Negative Quantifiers in L3 English to discriminate between two possible sources of transfer in the L3 grammar of Catalan/Spanish early bilinguals. Using a Self-Paced Reading technique, two groups of early bilinguals differing in their dominant language were tested: Catalan-dominant (n = 13) and Spanish-dominant (n = 9). Our results provide evidence that Language Dominance (LD) does not trump other traditionally-assumed variables in determining the source of transfer. Additionally, the data provide evidence that true beginners of an L3 are sensitive to morphosyntactic violations when their procedural knowledge of the L3 is examined, meaning that applying methodologies that tap procedural knowledge in L3 acquisition is viable and needed (cf. Rothman, Alemán Bañón, & González Alonso, 2015).