Health disparities related to sexual orientation are well documented and may be due to unequal access to a partner's employer-sponsored insurance (ESI). We provide the literature's first evaluation of legislation enacted by California in 2005 that required private employers within the state to treat employees in committed same-sex relationships in the same way as employees in different-sex marriages with respect to ESI. Our analysis uses data on sexual orientation, partnership, and health insurance from the 2001 to 2007 California Health Interview Surveys (CHIS). Prior to the reform, partnered gay men and lesbians were significantly less likely to have ESI in someone else's name than partnered heterosexuals. Pooling data from 2001 to 2007, we find that the reform had no effects on differences in insurance outcomes between gay and straight men. We find some evidence that the reform increased partnership, reduced full-time employment, and increased health insurance coverage among lesbians relative to heterosexual women. The increases in insurance coverage for lesbians are consistent with a role for expanded dependent ESI, suggesting that such policies may reduce sexual orientation-based insurance disparities among women.