From Longman Dictionary of Contemporary Englishmiddle-sizedˌmiddle-ˈsized adjective SIZEneither very large nor very small a middle-sized company
Examples from the Corpus
middle-sized• middle-sized cities• Information responsibility to others is increasingly understood, especially in middle-sized companies.• Apart from some smallholdings and, quite exceptionally, middle-sized farms, no re-privatization is envisaged.• The owner manager in the middle-sized firm is often a good example.• And that's one reason why I spent a middle-sized fortune in the most advanced form in Intelloid in the universe.• They have no bearing on postwar peace and stability in the area or stopping some other middle-sized gangster swallowing a weaker neighbour. 