Gruen's work lies at the intersection of ethical theory and ethical practice, with a particular focus on ethical issues that impact those often overlooked in traditional ethical investigations, e.g. women, people of color, non-human animals.
Most of her work is guided by two broad philosophical commitments. First, is the belief that ethics should be aimed primarily at enhancing well-being. She is usually considered a consequentialist, although my consequentialism is distinct from familiar forms of consequentialism in a number of ways. The second philosophical commitment that motivates and is expressed in her work is a commitment to justice, although her interest in justice tends to identify unjust distributions of benefits and burdens in areas that have previously been set to the side by others working on questions of justice.