The microenvironment has been shown to play an integral role in determining cell phenotype. However, the difficulties faced in accurately replicating structural features of the native microenvironment have hindered the progress towards creating suitable three-dimensional scaffolds for tissue engineering purposes. In this project, we incorporated PEG and PEG-diNHS into collagen gels to produce different structural features, allowing us to simulate a range of cell microenvironments. PEG resulted in aggregation of collagen fibrils producing a larger fiber diameter while PEG-diNHS acted as a cross-linker between fibrils creating smaller pore sizes. Based on confocal imaging data, L929 fibroblasts cultured on collagen-PEG gels were observed to have the highest levels of filamentous actin accompanied by an elongated morphology, in contrast to the rounded phenotype of fibroblasts from collagen-PEG-diNHS gels. These observations are a reflection of the in vivo wound healing process, in which changes in the ECM can induce fibroblasts to adopt different phenotypes that contribute to the recovery process.