With over 3,000 exoplanet discoveries to date, we have caught a glimpse of the broad diversity of exoplanets that span a range of masses, compositions, and orbital configurations. The next chapter in exoplanet exploration will focus on understanding the atmospheres of Jupiters to super-Earths, and we are now poised to begin large-scale atmospheric studies of exoplanets with current instruments on the Hubble Space Telescope (HST) via transmission spectroscopy. The HST Panchromatic Comparative Exoplanetology Treasury (PanCET) Program will assemble the first statistically significant sample of exoplanet atmospheric observations in the ultraviolet, optical, and infrared. As part of PanCET, we present precise optical to near-infrared (~0.29-4.5 microns) transmission spectra for two inflated hot Jupiters using combined HST and Spitzer transit observations. We compare the transmission spectra to a grid of 1D radiative-convective forward models and retrieve the planetary atmospheric properties. These broadband observations will constrain the atmospheric structure and chemical composition of the most favorable targets for atmospheric follow-up with JWST.