\usepackage {pstcol,pst-grad}
\begin{pspicture}(0,0)(3,2)\showgrid
 \psframe[framearc=0.25,
   fillstyle=gradient,
   gradangle=30,
   gradbegin=yellow,
   gradend=red]
   (0.5,0.5)(2.5,1.5)
\end{pspicture}