Mammalian cells are widely used to express genes for basic biology studies and biopharmaceuticals. Current methods for generation of engineered cell lines introduce high genomic and phenotypic diversity, which hamper studies of gene functions and discovery of novel cellular mechanisms. Here, we minimized clonal variation by integrating a landing pad for recombinase-mediated cassette exchange site-specifically into the genome of CHO cells using CRISPR and generated subclones expressing four different recombinant proteins. The subclones showed low clonal variation with high consistency in growth, transgene transcript levels and global transcriptional response to recombinant protein expression, enabling improved studies of the impact of transgenes on the host transcriptome. Little variation over time in subclone phenotypes and transcriptomes was observed when controlling environmental culture conditions. The platform enables robust comparative studies of genome engineered CHO cell lines and can be applied to other mammalian cells for diverse biological, biomedical and biotechnological applications.