This dataset contains count data for the number of each aphid life stage (nymphal stages 1-4 and adult) consumed by coccinellids in two lab-based experiments. The unit of observation (row) in the dataset is aphid life stage, therefore five rows correspond to one focal coccinellid. We experimentally assessed changes in feeding behaviour (prey preference and consumption rate) of native UK coccinellid species (Adalia bipunctata and Coccinella septempunctata), whose populations are, respectively, declining and stable, when exposed to the invasive intraguild predator, Harmonia axyridis. Experiment 1 determined the number of aphids consumed by each coccinellid larval stage in the absence of competition for each of the three coccinellid species. Experiment 2 then assessed the impact of competition on the number of aphids consumed by each coccinellid species. Full details about this nonGeographicDataset can be found at https://doi.org/10.5285/c8c3f4ef-889b-457a-a05b-1b2214d5802c